tiled image opacity works now with no overlapping regions at tile borders

src/webgldrawer.js

@@ -36,7 +36,7 @@
 
     // internal class Mat3: implements matrix operations
     // Modified from https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html
-class Mat3{
+   class Mat3{
        constructor(values){
            if(!values) {
                values = [
@@ -118,9 +118,9 @@ class Mat3{
            ]);
        }
 
-}
+   }
 
-/**
+   /**
     * @class WebGLDrawer
     * @memberof OpenSeadragon
     * @classdesc Default implementation of WebGLDrawer for an {@link OpenSeadragon.Viewer}.
@@ -131,7 +131,7 @@ class Mat3{
     * @param {Number} [options.debugGridColor] - See debugGridColor in {@link OpenSeadragon.Options} for details.
     */
 
-$.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
+    $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
         constructor(options){
            super(options);
 
@@ -144,7 +144,10 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
            this._gl = null;
            this._glLocs = null;
            this._glProgram = null;
-        this._glPositionBuffer = null;
+           this._glUnitQuadBuffer = null;
+           this._glFrameBuffer = null;
+           this._glTiledImageTexture = null;
+           this._glFramebufferToCanvasTransform = null;
            this._outputCanvas = null;
            this._outputContext = null;
            this._clippingCanvas = null;
@@ -193,8 +196,8 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             });
 
             // Delete all our created resources
-        gl.deleteBuffer(this._glPositionBuffer);
+            gl.deleteBuffer(this._glUnitQuadBuffer);
-
+            gl.deleteBuffer(this._glFrameBuffer);
             // TO DO: if/when render buffers or frame buffers are used, release them:
             // gl.deleteRenderbuffer(someRenderbuffer);
             // gl.deleteFramebuffer(someFramebuffer);
@@ -262,6 +265,7 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             * @param {Array} tiledImages Array of TiledImage objects to draw
             */
         draw(tiledImages){
+            let gl = this._gl;
             let viewport = {
                 bounds: this.viewport.getBoundsNoRotate(true),
                 center: this.viewport.getCenter(true),
@@ -275,21 +279,19 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             let rotMatrix = Mat3.makeRotation(-viewport.rotation);
             let viewMatrix = scaleMatrix.multiply(rotMatrix).multiply(posMatrix);
 
-        //iterate over tiled imagesget the list of tiles to draw
+            // clear the output canvas
             this._outputContext.clearRect(0, 0, this._outputCanvas.width, this._outputCanvas.height);
 
+
             // TO DO: further optimization is possible.
             // If no clipping and no composite operation, the tiled images
             // can all be drawn onto the rendering canvas at the same time, avoiding
             // unnecessary clearing and copying of the pixel data.
             // For now, I'm doing it this way to replicate full functionality
             // of the context2d drawer
-        tiledImages.forEach( (tiledImage, i) => {
-            // clear the rendering canvas
-            this._gl.clear(this._gl.COLOR_BUFFER_BIT);
 
-            // set opacity for this image
+            //iterate over tiled imagesget the list of tiles to draw
-            this._gl.uniform1f(this._glLocs.uOpacityMultiplier, tiledImage.opacity);
+            tiledImages.forEach( (tiledImage, i) => {
 
                 //get the list of tiles to draw
                 let tilesToDraw = tiledImage.getTilesToDraw();
@@ -298,9 +300,21 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
                     return;
                 }
 
+                // bind to the framebuffer for render-to-texture
+                gl.bindFramebuffer(gl.FRAMEBUFFER, this._glFrameBuffer);
+
+                // clear the buffer
+                gl.clear(gl.COLOR_BUFFER_BIT);
+
+                // set opacity for this image
+                gl.uniform1f(this._glLocs.uOpacityMultiplier, tiledImage.opacity);
+
+
+
                 let overallMatrix = viewMatrix;
 
                 let imageRotation = tiledImage.getRotation(true);
+                // if needed, handle the tiledImage being rotated
                 if( imageRotation % 360 !== 0){
                     let imageRotationMatrix = Mat3.makeRotation(-imageRotation * Math.PI / 180);
                     let imageCenter = tiledImage.getBoundsNoRotate(true).getCenter();
@@ -312,54 +326,48 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
                     overallMatrix = viewMatrix.multiply(localMatrix);
                 }
 
-            for(let i = 0; i < tilesToDraw.length; i++){
+                // iterate over tiles and draw each one to the buffer
-                let tile = tilesToDraw[i].tile;
+                for(let ti = 0; ti < tilesToDraw.length; ti++){
-                let texture = this._TextureMap.get(tile.getCanvasContext().canvas);
+                    let tile = tilesToDraw[ti].tile;
-                if(texture){
+                    let textureInfo = this._TextureMap.get(tile.getCanvasContext().canvas);
-                    this._drawTile(tile, tiledImage, texture, overallMatrix, tiledImage.opacity);
+                    if(textureInfo){
+                        this._drawTile(tile, tiledImage, textureInfo, overallMatrix, tiledImage.opacity);
                     } else {
                         // console.log('No tile info', tile);
                     }
                 }
 
-            // composite onto the output canvas, clipping if necessary
-            this._outputContext.save();
 
-            // set composite operation; ignore for first image drawn
+                // Draw from the Framebuffer onto the rendering canvas buffer
-            this._outputContext.globalCompositeOperation = i === 0 ? null : tiledImage.compositeOperation || this.viewer.compositeOperation;
-            if(tiledImage._croppingPolygons || tiledImage._clip){
-                this._renderToClippingCanvas(tiledImage);
-                this._outputContext.drawImage(this._clippingCanvas, 0, 0);
 
-            } else {
+                gl.flush(); // finish drawing to the texture
-                this._outputContext.drawImage(this._renderingCanvas, 0, 0);
+                gl.bindFramebuffer(gl.FRAMEBUFFER, null); // null means bind to the backbuffer for drawing
-            }
+                gl.bindTexture(gl.TEXTURE_2D, this._glTiledImageTexture); // bind the rendered texture to use
-            this._outputContext.restore();
+                gl.clear(gl.COLOR_BUFFER_BIT); // clear the back buffer
-            if(tiledImage.debugMode){
-                let colorIndex = this.viewer.world.getIndexOfItem(tiledImage) % this.debugGridColor.length;
-                let strokeStyle = this.debugGridColor[colorIndex];
-                let fillStyle = this.debugGridColor[colorIndex];
-                this._drawDebugInfo(tilesToDraw, tiledImage, strokeStyle, fillStyle);
-            }
 
-            if( this.viewer ){
+                // set up the matrix to draw the whole framebuffer to the entire clip space
-                /**
+                gl.uniformMatrix3fv(this._glLocs.uMatrix, false, this._glFramebufferToCanvasTransform);
-                 * Raised when a tiled image is drawn to the canvas. Only valid
+
-                 * for webgl drawer.
+                // reset texturebuffer to unit quad
-                 *
+                gl.bindBuffer(gl.ARRAY_BUFFER, this._glTextureBuffer);
-                 * @event tiled-image-drawn
+                gl.bufferData(gl.ARRAY_BUFFER, this._glUnitQuad, gl.DYNAMIC_DRAW);
-                 * @memberof OpenSeadragon.Viewer
+
-                 * @type {object}
+                // set opacity to the value for the current tiledImage
-                 * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised the event.
+                this._gl.uniform1f(this._glLocs.uOpacityMultiplier, tiledImage.opacity);
-                 * @property {OpenSeadragon.TiledImage} tiledImage - Which TiledImage is being drawn.
+                gl.drawArrays(gl.TRIANGLES, 0, 6);
-                 * @property {Array} tiles - An array of Tile objects that were drawn.
+
-                 * @property {?Object} userData - Arbitrary subscriber-defined object.
+                // iterate over any filters - filters can use this._glTiledImageTexture to get rendered data if desired
-                 */
+                let filters = this.filters || [];
-                this.viewer.raiseEvent( 'tiled-image-drawn', {
+                for(let fi = 0; fi < filters.length; fi++){
-                    tiledImage: tiledImage,
+                    let filter = this.filters[fi];
-                    tiles: tilesToDraw.map(info => info.tile),
+                    if(filter.apply){
-                });
+                        filter.apply(gl); // filter.apply should write data on top of the backbuffer (bound above)
                     }
+                }
+                gl.flush(); //make sure drawing to the output buffer of the rendering canvas is complete. Is this necessary?
+
+                // draw from the rendering canvas onto the output canvas, clipping/cropping if needed.
+                this._renderToOutputCanvas(tiledImage, tilesToDraw, i);
 
             });
 
@@ -395,20 +403,83 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
             context.restore();
         }
+        // private
         _getTextureDataFromTile(tile){
             return tile.getCanvasContext().canvas;
         }
 
-    // Private methods
+        /**
-    _drawTile(tile, tiledImage, texture, viewMatrix, imageOpacity){
+            * Draw data from the rendering canvas onto the output canvas, with clipping,
+            * cropping and/or debug info as requested.
+            * @private
+            * @param {OpenSeadragon.TiledImage} tiledImage - the tiledImage to draw
+            * @param {Array} tilesToDraw - array of objects containing tiles that were drawn
+            */
+        _renderToOutputCanvas(tiledImage, tilesToDraw, tiledImageIndex){
+            // composite onto the output canvas, clipping if necessary
+            this._outputContext.save();
+
+            // set composite operation; ignore for first image drawn
+            this._outputContext.globalCompositeOperation = tiledImageIndex === 0 ? null : tiledImage.compositeOperation || this.viewer.compositeOperation;
+            if(tiledImage._croppingPolygons || tiledImage._clip){
+                this._renderToClippingCanvas(tiledImage);
+                this._outputContext.drawImage(this._clippingCanvas, 0, 0);
+
+            } else {
+                this._outputContext.drawImage(this._renderingCanvas, 0, 0);
+            }
+            this._outputContext.restore();
+            if(tiledImage.debugMode){
+                let colorIndex = this.viewer.world.getIndexOfItem(tiledImage) % this.debugGridColor.length;
+                let strokeStyle = this.debugGridColor[colorIndex];
+                let fillStyle = this.debugGridColor[colorIndex];
+                this._drawDebugInfo(tilesToDraw, tiledImage, strokeStyle, fillStyle);
+            }
+
+            // Fire tiled-image-drawn event now that the data is on the output canvas
+            if( this.viewer ){
+                /**
+                    * Raised when a tiled image is drawn to the canvas. Only valid
+                    * for webgl drawer.
+                    *
+                    * @event tiled-image-drawn
+                    * @memberof OpenSeadragon.Viewer
+                    * @type {object}
+                    * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised the event.
+                    * @property {OpenSeadragon.TiledImage} tiledImage - Which TiledImage is being drawn.
+                    * @property {Array} tiles - An array of Tile objects that were drawn.
+                    * @property {?Object} userData - Arbitrary subscriber-defined object.
+                    */
+                this.viewer.raiseEvent( 'tiled-image-drawn', {
+                    tiledImage: tiledImage,
+                    tiles: tilesToDraw.map(info => info.tile),
+                });
+            }
+        }
+
+        // private
+        _drawTile(tile, tiledImage, textureInfo, viewMatrix, imageOpacity){
 
             let gl = this._gl;
+            let texture = textureInfo.texture;
+            let textureQuad = textureInfo.position;
+
+            // set the vertices into the non-overlapped portion of the texture
+            gl.bindBuffer(gl.ARRAY_BUFFER, this._glTextureBuffer);
+            gl.bufferData(gl.ARRAY_BUFFER, textureQuad, gl.DYNAMIC_DRAW);
+
+            // compute offsets for overlap
+            let overlapFraction = this._calculateOverlapFraction(tile, tiledImage);
+            let xOffset = tile.positionedBounds.width * overlapFraction.x;
+            let yOffset = tile.positionedBounds.height * overlapFraction.y;
 
             // x, y, w, h in viewport coords
-        let x = tile.positionedBounds.x;
+            let x = tile.positionedBounds.x + (tile.x === 0 ? 0 : xOffset);
-        let y = tile.positionedBounds.y;
+            let y = tile.positionedBounds.y + (tile.y === 0 ? 0 : yOffset);
-        let w = tile.positionedBounds.width;
+            let right = tile.positionedBounds.x + tile.positionedBounds.width - (tile.isRightMost ? 0 : xOffset);
-        let h = tile.positionedBounds.height;
+            let bottom = tile.positionedBounds.y + tile.positionedBounds.height - (tile.isBottomMost ? 0 : yOffset);
+            let w = right - x;
+            let h = bottom - y;
 
             let matrix = new Mat3([
                 w, 0, 0,
@@ -416,7 +487,6 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
                 x, y, 1,
             ]);
 
-
             if(tile.flipped){
                 // flip the tile around the center of the unit quad
                 let t1 = Mat3.makeTranslation(0.5, 0);
@@ -429,19 +499,17 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
             let overallMatrix = viewMatrix.multiply(matrix);
 
-        if(tile.opacity !== 1 && tile.x === 0 && tile.y === 0){
             // set opacity for this image
-            this._gl.uniform1f(this._glLocs.uOpacityMultiplier, imageOpacity * tile.opacity);
+            this._gl.uniform1f(this._glLocs.uOpacityMultiplier, tile.opacity); // imageOpacity *
-        }
 
             gl.uniformMatrix3fv(this._glLocs.uMatrix, false, overallMatrix.values);
             gl.bindTexture(gl.TEXTURE_2D, texture);
 
             if(this.continuousTileRefresh){
-            // Upload the image into the texture.
+                // Upload the image into the texture (already bound to TEXTURE_2D above)
                 let tileContext = tile.getCanvasContext();
                 this._raiseTileDrawingEvent(tiledImage, this._outputContext, tile, tileContext);
-            this._uploadImageData(tileContext);
+                this._uploadImageData(tileContext, tile, tiledImage);
             }
 
 
@@ -455,18 +523,17 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             }
 
             const vertexShaderProgram = `
-        attribute vec2 a_position;
+            attribute vec2 a_output_position;
+            attribute vec2 a_texture_position;
 
             uniform mat3 u_matrix;
 
             varying vec2 v_texCoord;
 
             void main() {
-        gl_Position = vec4(u_matrix * vec3(a_position, 1), 1);
+            gl_Position = vec4(u_matrix * vec3(a_output_position, 1), 1);
 
-        // because we're using a unit quad we can just use
+            v_texCoord = a_texture_position;
-        // the same data for our texcoords.
-        v_texCoord = a_position;
             }
             `;
 
@@ -484,7 +551,7 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
             void main() {
             gl_FragColor = texture2D(u_image, v_texCoord);
-        // gl_FragColor *= u_opacity_multiplier;
+            gl_FragColor *= u_opacity_multiplier;
             }
             `;
             let gl = this._gl;
@@ -494,24 +561,69 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
 
             this._glLocs = {
-            aPosition: gl.getAttribLocation(this._glProgram, 'a_position'),
+                aOutputPosition: gl.getAttribLocation(this._glProgram, 'a_output_position'),
+                aTexturePosition: gl.getAttribLocation(this._glProgram, 'a_texture_position'),
                 uMatrix: gl.getUniformLocation(this._glProgram, 'u_matrix'),
                 uImage: gl.getUniformLocation(this._glProgram, 'u_image'),
                 uOpacityMultiplier: gl.getUniformLocation(this._glProgram, 'u_opacity_multiplier')
             };
 
-        // provide texture coordinates for the rectangle.
+            this._glUnitQuad = this._makeQuadVertexBuffer(0, 1, 0, 1);
-        this._glPositionBuffer = gl.createBuffer(); //keep reference to clear it later
+            // provide texture coordinates for the rectangle in output space.
-        gl.bindBuffer(gl.ARRAY_BUFFER, this._glPositionBuffer);
+            this._glUnitQuadBuffer = gl.createBuffer(); //keep reference to clear it later
-        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
+            gl.bindBuffer(gl.ARRAY_BUFFER, this._glUnitQuadBuffer);
-            0.0, 0.0,
+            gl.bufferData(gl.ARRAY_BUFFER, this._glUnitQuad, gl.STATIC_DRAW);
-            1.0, 0.0,
+            gl.enableVertexAttribArray(this._glLocs.aOutputPosition);
-            0., 1.0,
+            gl.vertexAttribPointer(this._glLocs.aOutputPosition, 2, gl.FLOAT, false, 0, 0);
-            0.0, 1.0,
+
-            1.0, 0.0,
+            // provide texture coordinates for the rectangle in image (texture) space.
-            1.0, 1.0]), gl.STATIC_DRAW);
+            this._glTextureBuffer = gl.createBuffer(); //keep reference to clear it later
-        gl.enableVertexAttribArray(this._glLocs.aPosition);
+            gl.bindBuffer(gl.ARRAY_BUFFER, this._glTextureBuffer);
-        gl.vertexAttribPointer(this._glLocs.aPosition, 2, gl.FLOAT, false, 0, 0);
+            gl.bufferData(gl.ARRAY_BUFFER, this._glUnitQuad, gl.DYNAMIC_DRAW); // use unit quad to start, will be updated per tile
+            gl.enableVertexAttribArray(this._glLocs.aTexturePosition);
+            gl.vertexAttribPointer(this._glLocs.aTexturePosition, 2, gl.FLOAT, false, 0, 0);
+
+            // setup the framebuffer
+            this._glTiledImageTexture = gl.createTexture();
+            gl.bindTexture(gl.TEXTURE_2D, this._glTiledImageTexture);
+            gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, this._renderingCanvas.width, this._renderingCanvas.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+            this._glFrameBuffer = gl.createFramebuffer();
+            gl.bindFramebuffer(gl.FRAMEBUFFER, this._glFrameBuffer);
+            gl.framebufferTexture2D(
+                gl.FRAMEBUFFER,
+                gl.COLOR_ATTACHMENT0,  // attach texture as COLOR_ATTACHMENT0
+                gl.TEXTURE_2D,         // attach a 2D texture
+                this._glTiledImageTexture,           // the texture to attach
+                0
+            );
+
+            this._glFramebufferToCanvasTransform = Mat3.makeScaling(2, 2).multiply(Mat3.makeTranslation(-0.5, -0.5)).values;
+
+
+        }
+
+        _resizeRenderer(){
+            let gl = this._gl;
+            let w = this._renderingCanvas.width;
+            let h = this._renderingCanvas.height;
+            gl.viewport(0, 0, w, h);
+
+            //release the old texture
+            gl.deleteTexture(this._glTiledImageTexture);
+            //create a new texture and set it up
+            this._glTiledImageTexture = gl.createTexture();
+            gl.bindTexture(gl.TEXTURE_2D, this._glTiledImageTexture);
+            gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, w, h, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+
+            //bind the frame buffer to the new texture
+            gl.bindFramebuffer(gl.FRAMEBUFFER, this._glFrameBuffer);
+            gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, this._glTiledImageTexture, 0);
 
         }
 
@@ -549,25 +661,60 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
                 _this._renderingCanvas.style.height = _this._outputCanvas.clientHeight + 'px';
                 _this._renderingCanvas.width = _this._clippingCanvas.width = _this._outputCanvas.width;
                 _this._renderingCanvas.height = _this._clippingCanvas.height = _this._outputCanvas.height;
-            _this._gl.viewport(0, 0, _this._renderingCanvas.width, _this._renderingCanvas.height);
+
+                // important - update the size of the rendering viewport!
+                _this._resizeRenderer();
             });
         }
 
+        _makeQuadVertexBuffer(left, right, top, bottom){
+            return new Float32Array([
+                left, bottom,
+                right, bottom,
+                left, top,
+                left, top,
+                right, bottom,
+                right, top]);
+        }
+
 
         _tileReadyHandler(event){
             let tile = event.tile;
+            let tiledImage = event.tiledImage;
             let tileContext = tile.getCanvasContext();
             let canvas = tileContext.canvas;
-        let texture = this._TextureMap.get(canvas);
+            let textureInfo = this._TextureMap.get(canvas);
 
             // if this is a new image for us, create a texture
-        if(!texture){
+            if(!textureInfo){
                 let gl = this._gl;
 
                 // create a gl Texture for this tile and bind the canvas with the image data
-            texture = gl.createTexture();
+                let texture = gl.createTexture();
+                let position;
+                let overlap = tiledImage.source.tileOverlap;
+                if( overlap > 0){
+                    // calculate the normalized position of the rect to actually draw
+                    // discarding overlap.
+                    let overlapFraction = this._calculateOverlapFraction(tile, tiledImage);
+
+                    let left = tile.x === 0 ? 0 : overlapFraction.x;
+                    let top = tile.y === 0 ? 0 : overlapFraction.y;
+                    let right = tile.isRightMost ? 1 : 1 - overlapFraction.x;
+                    let bottom = tile.isBottomMost ? 1 : 1 - overlapFraction.y;
+                    position = this._makeQuadVertexBuffer(left, right, top, bottom);
+                } else {
+                    // no overlap: this texture can use the unit quad as it's position data
+                    position = this._glUnitQuad;
+                }
+
+                let textureInfo = {
+                    texture: texture,
+                    position: position,
+                };
+
                 // add it to our _TextureMap
-            this._TextureMap.set(canvas, texture);
+                this._TextureMap.set(canvas, textureInfo);
 
                 gl.bindTexture(gl.TEXTURE_2D, texture);
                 // Set the parameters so we can render any size image.
@@ -583,17 +730,29 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
         }
 
+        _calculateOverlapFraction(tile, tiledImage){
+            let overlap = tiledImage.source.tileOverlap;
+            let nativeWidth = tile.sourceBounds.width; // in pixels
+            let nativeHeight = tile.sourceBounds.height; // in pixels
+            let overlapWidth  = (tile.x === 0 ? 0 : overlap) + (tile.isRightMost ? 0 : overlap); // in pixels
+            let overlapHeight = (tile.y === 0 ? 0 : overlap) + (tile.isBottomMost ? 0 : overlap); // in pixels
+            let widthOverlapFraction = overlap / (nativeWidth + overlapWidth); // as a fraction of image including overlap
+            let heightOverlapFraction = overlap / (nativeHeight + overlapHeight); // as a fraction of image including overlap
+            return {
+                x: widthOverlapFraction,
+                y: heightOverlapFraction
+            };
+        }
+
         _uploadImageData(tileContext){
+
             let gl = this._gl;
-        try{
             let canvas = tileContext.canvas;
-            if(!canvas){
+
-                throw('Tile context does not have a canvas', tileContext);
+            // This depends on gl.TEXTURE_2D being bound to the texture
-            }
+            // associated with this canvas before calling this function
             gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, canvas);
-        } catch(e) {
+
-            $.console.error('Error uploading canvas data to webgl', e);
-        }
         }
 
         _imageUnloadedHandler(event){
@@ -602,12 +761,17 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
         }
 
         _cleanupImageData(tileCanvas){
-        let texture = this._TextureMap.get(tileCanvas);
+            let textureInfo = this._TextureMap.get(tileCanvas);
             //remove from the map
             this._TextureMap.delete(tileCanvas);
 
             //release the texture from the GPU
-        this._gl.deleteTexture(texture);
+            if(textureInfo){
+                this._gl.deleteTexture(textureInfo.texture);
+            }
+
+            // release the position buffer from the GPU
+            // TO DO: do this!
         }
         // private
         // necessary for clip testing to pass (test uses spyOnce(drawer._setClip))
@@ -810,8 +974,8 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
         // modified from https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Adding_2D_content_to_a_WebGL_context
         static initShaderProgram(gl, vsSource, fsSource) {
-        const vertexShader = this.loadShader(gl, gl.VERTEX_SHADER, vsSource);
+            const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
-        const fragmentShader = this.loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
+            const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
 
             // Create the shader program
 
@@ -832,13 +996,8 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
             }
 
             return shaderProgram;
-    }
 
-    //
+            function loadShader(gl, type, source) {
-    // creates a shader of the given type, uploads the source and
-    // compiles it.
-    //
-    static loadShader(gl, type, source) {
                     const shader = gl.createShader(type);
 
                     // Send the source to the shader object
@@ -861,7 +1020,18 @@ $.WebGLDrawer = class WebGLDrawer extends OpenSeadragon.DrawerBase{
 
                 return shader;
             }
-};
+        }
+
+    };
+
+    // $.WebGLDrawer.Filter = class{
+    //     constructor(gl){
+    //         this.gl = gl;
+    //     }
+    //     apply(){
+
+    //     }
+    // };
 
 
 }( OpenSeadragon ));

test/demo/drawercomparison.html

@@ -1,14 +1,13 @@
 <!DOCTYPE html>
 <html>
 <head>
-    <title>OSD-ThreeJS</title>
+    <title>Drawer Comparison Demo</title>
     <script type="text/javascript" src='../../build/openseadragon/openseadragon.js'></script>
     <script type="text/javascript" src='../lib/jquery-1.9.1.min.js'></script>
     <script type="text/javascript" src='../lib/jquery-ui-1.10.2/js/jquery-ui-1.10.2.min.js'></script>
     <link rel="stylesheet" href="../lib/jquery-ui-1.10.2/css/smoothness/jquery-ui-1.10.2.min.css">
 
-    </script>
+    <script type="module" src="./drawercomparison.js"></script>
-    <script type="module" src="./webgl.js"></script>
     <style type="text/css">
         .content{
             max-width:960px;
@@ -62,7 +61,7 @@
 <body>
     <div class="content">
 
-        <h2>Compare behavior of <strong>Context2d</strong> and <strong>WebGL</strong> (via three.js) drawers</h2>
+        <h2>Compare behavior of <strong>Context2d</strong> and <strong>WebGL</strong> drawers</h2>
         <div class="mirrored">
             <div>
                 <h3>Context2d drawer (default in OSD &lt;= 4.1.0)</h3>

test/demo/drawercomparison.js

@@ -15,7 +15,7 @@ const labels = {
 }
 
 //Double viewer setup for comparison - Context2dDrawer and WebGLDrawer
-
+// viewer1: context2d drawer
 let viewer1 = window.viewer1 = OpenSeadragon({
     id: "context2d",
     prefixUrl: "../../build/openseadragon/images/",
@@ -29,6 +29,7 @@ let viewer1 = window.viewer1 = OpenSeadragon({
     blendTime:0
 });
 
+// viewer2: webgl drawer
 let viewer2 = window.viewer2 = OpenSeadragon({
     id: "webgl",
     prefixUrl: "../../build/openseadragon/images/",
@@ -39,9 +40,26 @@ let viewer2 = window.viewer2 = OpenSeadragon({
     ajaxWithCredentials: false,
     // maxImageCacheCount: 30,
     drawer:'webgl',
-    blendTime:0
+    blendTime:0,
 });
 
+// viewer3: html drawer
+var viewer3 = window.viewer3 = OpenSeadragon({
+    id: "htmldrawer",
+    drawer:'html',
+    blendTime:2,
+    prefixUrl: "../../build/openseadragon/images/",
+    minZoomImageRatio:0.01,
+    customDrawer: OpenSeadragon.HTMLDrawer,
+    tileSources: [sources['leaves'], sources['rainbow'], sources['duomo']],
+    sequenceMode: true,
+    crossOriginPolicy: 'Anonymous',
+    ajaxWithCredentials: false
+});
+
+
+
+
 // Sync navigation of viewer1 and viewer 2
 var viewer1Leading = false;
 var viewer2Leading = false;
@@ -82,22 +100,6 @@ viewer1.addHandler('flip', viewer1Handler);
 viewer2.addHandler('flip', viewer2Handler);
 
 
-// Single viewer showing how to use plugin Drawer via configuration
-// Also shows sequence mode
-var viewer3 = window.viewer3 = OpenSeadragon({
-    id: "htmldrawer",
-    drawer:'html',
-    blendTime:2,
-    prefixUrl: "../../build/openseadragon/images/",
-    minZoomImageRatio:0.01,
-    customDrawer: OpenSeadragon.HTMLDrawer,
-    tileSources: [sources['leaves'], sources['rainbow'], sources['duomo']],
-    sequenceMode: true,
-    crossOriginPolicy: 'Anonymous',
-    ajaxWithCredentials: false
-});
-
-
 $('#image-picker').sortable({
     update: function(event, ui){
         let thisItem = ui.item.find('.toggle').data('item1');

test/demo/webglfiltering.html

@@ -0,0 +1,105 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>WebGL Demo</title>
+    <script type="text/javascript" src='../../build/openseadragon/openseadragon.js'></script>
+    <script type="text/javascript" src='../lib/jquery-1.9.1.min.js'></script>
+    <script type="text/javascript" src='../lib/jquery-ui-1.10.2/js/jquery-ui-1.10.2.min.js'></script>
+    <link rel="stylesheet" href="../lib/jquery-ui-1.10.2/css/smoothness/jquery-ui-1.10.2.min.css">
+    <script type="text/javascript" src="./webgldemodrawer.js"></script>
+    <script type="module" src="./webglfiltering.js"></script>
+    <style type="text/css">
+        .content{
+            max-width:960px;
+            margin: 0 auto;
+        }
+        .side-by-side{
+            display:grid;
+            grid-template-columns:50% 50%;
+            gap: 2em;
+        }
+        .viewer-container {
+            /* width: 600px;
+            height: 400px; */
+            aspect-ratio: 4 / 3;
+            border: thin gray solid;
+            position:relative;
+        }
+        .example-code{
+            background-color:tan;
+            border: thin black solid;
+            padding:10px;
+            display:inline-block;
+            width:95%;
+        }
+        .description pre{
+            display:inline-block;
+            background-color:gainsboro;
+            padding:0;
+            margin:0;
+        }
+
+        .image-options{
+            display: grid;
+            grid-template-columns: 2em 9em 1fr;
+            padding:3px;
+            border: thin gray solid;
+        }
+        .option-grid{
+            display: grid;
+            grid-template-columns: 7em 7em 10em 10em 10em;
+            /* grid-template-columns: repeat(5, auto); */
+        }
+        .image-options input[type=number]{
+            width: 5em;
+        }
+        .image-options select{
+            width: 5em;
+        }
+    </style>
+</head>
+<body>
+    <div class="content">
+
+        <h2>WebGLDrawer demonstration</h2>
+        <div class="side-by-side">
+            <div>
+                <div id="webgl" class="viewer-container"></div>
+            </div>
+        </div>
+
+
+        <div id="image-picker">
+            <h3>Image options (drag and drop to re-order images)</h3>
+
+
+        </div>
+
+        <h2>Example code</h2>
+        <div>
+            <div>
+                <div class="description">
+                    Drawer options are shown below.
+                </div>
+                <pre class="example-code">
+    let viewer = OpenSeadragon({
+        ...
+        drawer: 'webgl',
+        drawerOptions: {
+            webgl: {
+                programs: [],
+            }
+        }
+        ...
+    });
+                </pre>
+            </div>
+            <div id="htmldrawer" class="viewer-container"></div>
+        </div>
+    </div>
+
+
+
+</body>
+</html>
+

test/demo/webglfiltering.js

@@ -0,0 +1,298 @@
+const sources = {
+    "rainbow":"../data/testpattern.dzi",
+    "leaves":"../data/iiif_2_0_sizes/info.json",
+    "bblue":{
+        type:'image',
+        url: "../data/BBlue.png",
+    },
+    "duomo":"https://openseadragon.github.io/example-images/duomo/duomo.dzi",
+}
+const labels = {
+    rainbow: 'Rainbow Grid',
+    leaves: 'Leaves',
+    bblue: 'Blue B',
+    duomo: 'Duomo',
+}
+
+// viewer1: context2d drawer
+let viewer1 = window.viewer1 = OpenSeadragon({
+    id: "webgl",
+    prefixUrl: "../../build/openseadragon/images/",
+    minZoomImageRatio:0.01,
+    maxZoomPixelRatio:100,
+    smoothTileEdgesMinZoom:1.1,
+    crossOriginPolicy: 'Anonymous',
+    ajaxWithCredentials: false,
+    // maxImageCacheCount: 30,
+    drawer:OpenSeadragon.WebGL2Drawer,
+    blendTime:0,
+    drawerOptions:{
+        webgl:{
+            programs:[makeRedFilter()],
+        }
+    }
+});
+
+setupImageControls();
+
+
+
+class ColorChanelFilter {
+    constructor() {
+        this.red = 1;
+        this.blue = 1;
+        this.green = 1;
+
+        this.program = null;
+    }
+    createProgram(gl){
+        this.program = OpenSeadragon.WebGLDrawer.initShaderProgram(gl, this.getVertexShaderCode(), this.getFragmentShaderCode());
+    }
+    apply(gl, tiledImageTexture, tiledImage){
+
+    }
+    getVertexShaderCode(){
+        return `
+            attribute vec2 a_output_position;
+            attribute vec2 a_texture_position;
+
+            uniform mat3 u_matrix;
+
+            varying vec2 v_texCoord;
+
+            void main() {
+                gl_Position = vec4(u_matrix * vec3(a_output_position, 1), 1);
+
+                v_texCoord = a_texture_position;
+            }
+        `;
+    }
+    getFragmentShaderCode(){
+        return `
+            precision mediump float;
+
+            // our texture
+            uniform sampler2D u_image;
+
+            // the texCoords passed in from the vertex shader.
+            varying vec2 v_texCoord;
+
+            // the opacity multiplier for the image
+            uniform vec3 color_multiplier;
+
+            void main() {
+                gl_FragColor = texture2D(u_image, v_texCoord);
+                gl_FragColor *= vec4(color_multiplier, 1);
+             }
+        `;
+    }
+
+}
+
+
+
+
+
+function setupImageControls(){
+
+$('#image-picker').sortable({
+    update: function(event, ui){
+        let thisItem = ui.item.find('.toggle').data('item1');
+        let items = $('#image-picker input.toggle:checked').toArray().map(item=>$(item).data('item1'));
+        let newIndex = items.indexOf(thisItem);
+        if(thisItem){
+            viewer1.world.setItemIndex(thisItem, newIndex);
+        }
+    }
+});
+
+Object.keys(sources).forEach((key, index)=>{
+    let element = makeImagePickerElement(key, labels[key])
+    $('#image-picker').append(element);
+    if(index === 0){
+        element.find('.toggle').prop('checked',true);
+    }
+})
+
+$('#image-picker input.toggle').on('change',function(){
+    let data = $(this).data();
+    if(this.checked){
+        addTileSource(viewer1, data.image, this);
+    } else {
+        if(data.item1){
+            viewer1.world.removeItem(data.item1);
+            $(this).data({item1: null});
+        }
+    }
+}).trigger('change');
+
+$('#image-picker input:not(.toggle)').on('change',function(){
+    let data = $(this).data();
+    let value = $(this).val();
+    let tiledImage1 = $(`#image-picker input.toggle[data-image=${data.image}]`).data('item1');
+    updateTiledImage(tiledImage1, data, value, this);
+});
+
+function updateTiledImage(tiledImage, data, value, item){
+    if(tiledImage){
+        //item = tiledImage
+        let field = data.field;
+        if(field == 'x'){
+            let bounds = tiledImage.getBoundsNoRotate();
+            let position = new OpenSeadragon.Point(Number(value), bounds.y);
+            tiledImage.setPosition(position);
+        } else if ( field == 'y'){
+            let bounds = tiledImage.getBoundsNoRotate();
+            let position = new OpenSeadragon.Point(bounds.x, Number(value));
+            tiledImage.setPosition(position);
+        } else if (field == 'width'){
+            tiledImage.setWidth(Number(value));
+        } else if (field == 'degrees'){
+            tiledImage.setRotation(Number(value));
+        } else if (field == 'opacity'){
+            tiledImage.setOpacity(Number(value));
+        } else if (field == 'flipped'){
+            tiledImage.setFlip($(item).prop('checked'));
+        } else if (field == 'cropped'){
+            if( $(item).prop('checked') ){
+                let croppingPolygons = [ [{x:200, y:200}, {x:800, y:200}, {x:500, y:800}] ];
+                tiledImage.setCroppingPolygons(croppingPolygons);
+            } else {
+                tiledImage.resetCroppingPolygons();
+            }
+        } else if (field == 'clipped'){
+            if( $(item).prop('checked') ){
+                let clipRect = new OpenSeadragon.Rect(2000, 0, 3000, 4000);
+                tiledImage.setClip(clipRect);
+            } else {
+                tiledImage.setClip(null);
+            }
+        }
+        else if (field == 'debug'){
+            if( $(item).prop('checked') ){
+                tiledImage.debugMode = true;
+            } else {
+                tiledImage.debugMode = false;
+            }
+        }
+    }
+}
+
+$('.image-options select[data-field=composite]').append(getCompositeOperationOptions()).on('change',function(){
+    let data = $(this).data();
+    let tiledImage1 = $(`#image-picker input.toggle[data-image=${data.image}]`).data('item1');
+    if(tiledImage1){
+        tiledImage1.setCompositeOperation(this.value == 'null' ? null : this.value);
+    }
+    let tiledImage2 = $(`#image-picker input.toggle[data-image=${data.image}]`).data('item2');
+    if(tiledImage2){
+        tiledImage2.setCompositeOperation(this.value == 'null' ? null : this.value);
+    }
+}).trigger('change');
+
+$('.image-options select[data-field=wrapping]').append(getWrappingOptions()).on('change',function(){
+    let data = $(this).data();
+    let tiledImage = $(`#image-picker input.toggle[data-image=${data.image}]`).data('item1');
+    if(tiledImage){
+        switch(this.value){
+            case "None": tiledImage.wrapHorizontal = tiledImage.wrapVertical = false; break;
+            case "Horizontal": tiledImage.wrapHorizontal = true; tiledImage.wrapVertical = false; break;
+            case "Vertical": tiledImage.wrapHorizontal = false; tiledImage.wrapVertical = true; break;
+            case "Both": tiledImage.wrapHorizontal = tiledImage.wrapVertical = true; break;
+        }
+        tiledImage.viewer.raiseEvent('opacity-change');//trigger a redraw for the webgl renderer. TODO: fix this hack.
+    }
+    tiledImage = $(`#image-picker input.toggle[data-image=${data.image}]`).data('item2');
+    if(tiledImage){
+        switch(this.value){
+            case "None": tiledImage.wrapHorizontal = tiledImage.wrapVertical = false; break;
+            case "Horizontal": tiledImage.wrapHorizontal = true; tiledImage.wrapVertical = false; break;
+            case "Vertical": tiledImage.wrapHorizontal = false; tiledImage.wrapVertical = true; break;
+            case "Both": tiledImage.wrapHorizontal = tiledImage.wrapVertical = true; break;
+        }
+        tiledImage.viewer.raiseEvent('opacity-change');//trigger a redraw for the webgl renderer. TODO: fix this hack.
+    }
+}).trigger('change');
+
+function getWrappingOptions(){
+    let opts = ['None', 'Horizontal', 'Vertical', 'Both'];
+    let elements = opts.map((opt, i)=>{
+        let el = $('<option>',{value:opt}).text(opt);
+        if(i===0){
+            el.attr('selected',true);
+        }
+        return el[0];
+        // $('.image-options select').append(el);
+    });
+    return $(elements);
+}
+function getCompositeOperationOptions(){
+    let opts = [null,'source-over','source-in','source-out','source-atop',
+                'destination-over','destination-in','destination-out','destination-atop',
+                'lighten','darken','copy','xor','multiply','screen','overlay','color-dodge',
+                'color-burn','hard-light','soft-light','difference','exclusion',
+                'hue','saturation','color','luminosity'];
+    let elements = opts.map((opt, i)=>{
+        let el = $('<option>',{value:opt}).text(opt);
+        if(i===0){
+            el.attr('selected',true);
+        }
+        return el[0];
+        // $('.image-options select').append(el);
+    });
+    return $(elements);
+
+}
+
+function addTileSource(viewer, image, checkbox){
+    let options = $(`#image-picker input[data-image=${image}][type=number]`).toArray().reduce((acc, input)=>{
+        let field = $(input).data('field');
+        if(field){
+            acc[field] = Number(input.value);
+        }
+        return acc;
+    }, {});
+
+    options.flipped = $(`#image-picker input[data-image=${image}][data-type=flipped]`).prop('checked');
+
+    let items = $('#image-picker input.toggle:checked').toArray();
+    let insertionIndex = items.indexOf(checkbox);
+
+    let tileSource = sources[image];
+    if(tileSource){
+        viewer&&viewer.addTiledImage({tileSource: tileSource, ...options, index: insertionIndex});
+        viewer&&viewer.world.addOnceHandler('add-item',function(ev){
+            let item = ev.item;
+            let field = viewer === viewer1 ? 'item1' : 'item2';
+            $(checkbox).data(field,item);
+            item.source.hasTransparency = ()=>true; //simulate image with transparency, to show seams in default renderer
+        });
+    }
+}
+
+function makeImagePickerElement(key, label){
+    return $(`<div class="image-options">
+        <span class="ui-icon ui-icon-arrowthick-2-n-s"></span>
+        <label><input type="checkbox" data-image="" class="toggle"> __title__</label>
+        <div class="option-grid">
+            <label>X: <input type="number" value="0" data-image="" data-field="x"> </label>
+            <label>Y: <input type="number" value="0" data-image="" data-field="y"> </label>
+            <label>Width: <input type="number" value="1" data-image="" data-field="width" min="0"> </label>
+            <label>Degrees: <input type="number" value="0" data-image="" data-field="degrees"> </label>
+            <label>Opacity: <input type="number" value="1" data-image="" data-field="opacity" min="0" max="1" step="0.2"> </label>
+            <label>Flipped: <input type="checkbox" data-image="" data-field="flipped"></label>
+            <label>Cropped: <input type="checkbox" data-image="" data-field="cropped"></label>
+            <label>Debug: <input type="checkbox" data-image="" data-field="debug"></label>
+            <label>Composite: <select data-image="" data-field="composite"></select></label>
+            <label>Wrapping: <select data-image="" data-field="wrapping"></select></label>
+        </div>
+
+    </div>`.replaceAll('data-image=""', `data-image="${key}"`).replace('__title__', label));
+
+}
+}
+
+
+
+
+