From a60abd97937f8e5997a7c4e6e0937c79bb644702 Mon Sep 17 00:00:00 2001 From: Mario Colque Date: Sat, 8 Mar 2014 03:24:28 -0300 Subject: [PATCH] added a new library for fir canvas on ios/safari --- .../ios-imagefile-megapixel/megapix-image.js | 254 ++++++++++++++++++ 1 file changed, 254 insertions(+) create mode 100644 public/src/js/ios-imagefile-megapixel/megapix-image.js diff --git a/public/src/js/ios-imagefile-megapixel/megapix-image.js b/public/src/js/ios-imagefile-megapixel/megapix-image.js new file mode 100644 index 0000000..ad7b278 --- /dev/null +++ b/public/src/js/ios-imagefile-megapixel/megapix-image.js @@ -0,0 +1,254 @@ +/** + * Mega pixel image rendering library for iOS6 Safari + * + * Fixes iOS6 Safari's image file rendering issue for large size image (over mega-pixel), + * which causes unexpected subsampling when drawing it in canvas. + * By using this library, you can safely render the image with proper stretching. + * + * Copyright (c) 2012 Shinichi Tomita + * Released under the MIT license + */ +(function() { + + /** + * Detect subsampling in loaded image. + * In iOS, larger images than 2M pixels may be subsampled in rendering. + */ + function detectSubsampling(img) { + var iw = img.naturalWidth, ih = img.naturalHeight; + if (iw * ih > 1024 * 1024) { // subsampling may happen over megapixel image + var canvas = document.createElement('canvas'); + canvas.width = canvas.height = 1; + var ctx = canvas.getContext('2d'); + ctx.drawImage(img, -iw + 1, 0); + // subsampled image becomes half smaller in rendering size. + // check alpha channel value to confirm image is covering edge pixel or not. + // if alpha value is 0 image is not covering, hence subsampled. + return ctx.getImageData(0, 0, 1, 1).data[3] === 0; + } else { + return false; + } + } + + /** + * Detecting vertical squash in loaded image. + * Fixes a bug which squash image vertically while drawing into canvas for some images. + */ + function detectVerticalSquash(img, iw, ih) { + var canvas = document.createElement('canvas'); + canvas.width = 1; + canvas.height = ih; + var ctx = canvas.getContext('2d'); + ctx.drawImage(img, 0, 0); + var data = ctx.getImageData(0, 0, 1, ih).data; + // search image edge pixel position in case it is squashed vertically. + var sy = 0; + var ey = ih; + var py = ih; + while (py > sy) { + var alpha = data[(py - 1) * 4 + 3]; + if (alpha === 0) { + ey = py; + } else { + sy = py; + } + py = (ey + sy) >> 1; + } + var ratio = (py / ih); + return (ratio===0)?1:ratio; + } + + /** + * Rendering image element (with resizing) and get its data URL + */ + function renderImageToDataURL(img, options, doSquash) { + var canvas = document.createElement('canvas'); + renderImageToCanvas(img, canvas, options, doSquash); + return canvas.toDataURL("image/jpeg", options.quality || 0.8); + } + + /** + * Rendering image element (with resizing) into the canvas element + */ + function renderImageToCanvas(img, canvas, options, doSquash) { + var iw = img.naturalWidth, ih = img.naturalHeight; + var width = options.width, height = options.height; + var ctx = canvas.getContext('2d'); + ctx.save(); + transformCoordinate(canvas, width, height, options.orientation); + var subsampled = detectSubsampling(img); + if (subsampled) { + iw /= 2; + ih /= 2; + } + var d = 1024; // size of tiling canvas + var tmpCanvas = document.createElement('canvas'); + tmpCanvas.width = tmpCanvas.height = d; + var tmpCtx = tmpCanvas.getContext('2d'); + var vertSquashRatio = doSquash ? detectVerticalSquash(img, iw, ih) : 1; + var dw = Math.ceil(d * width / iw); + var dh = Math.ceil(d * height / ih / vertSquashRatio); + var sy = 0; + var dy = 0; + while (sy < ih) { + var sx = 0; + var dx = 0; + while (sx < iw) { + tmpCtx.clearRect(0, 0, d, d); + tmpCtx.drawImage(img, -sx, -sy); + ctx.drawImage(tmpCanvas, 0, 0, d, d, dx, dy, dw, dh); + sx += d; + dx += dw; + } + sy += d; + dy += dh; + } + ctx.restore(); + tmpCanvas = tmpCtx = null; + } + + /** + * Transform canvas coordination according to specified frame size and orientation + * Orientation value is from EXIF tag + */ + function transformCoordinate(canvas, width, height, orientation) { + switch (orientation) { + case 5: + case 6: + case 7: + case 8: + canvas.width = height; + canvas.height = width; + break; + default: + canvas.width = width; + canvas.height = height; + } + var ctx = canvas.getContext('2d'); + switch (orientation) { + case 2: + // horizontal flip + ctx.translate(width, 0); + ctx.scale(-1, 1); + break; + case 3: + // 180 rotate left + ctx.translate(width, height); + ctx.rotate(Math.PI); + break; + case 4: + // vertical flip + ctx.translate(0, height); + ctx.scale(1, -1); + break; + case 5: + // vertical flip + 90 rotate right + ctx.rotate(0.5 * Math.PI); + ctx.scale(1, -1); + break; + case 6: + // 90 rotate right + ctx.rotate(0.5 * Math.PI); + ctx.translate(0, -height); + break; + case 7: + // horizontal flip + 90 rotate right + ctx.rotate(0.5 * Math.PI); + ctx.translate(width, -height); + ctx.scale(-1, 1); + break; + case 8: + // 90 rotate left + ctx.rotate(-0.5 * Math.PI); + ctx.translate(-width, 0); + break; + default: + break; + } + } + + + /** + * MegaPixImage class + */ + function MegaPixImage(srcImage) { + if (window.Blob && srcImage instanceof Blob) { + var img = new Image(); + var URL = window.URL && window.URL.createObjectURL ? window.URL : + window.webkitURL && window.webkitURL.createObjectURL ? window.webkitURL : + null; + if (!URL) { throw Error("No createObjectURL function found to create blob url"); } + img.src = URL.createObjectURL(srcImage); + this.blob = srcImage; + srcImage = img; + } + if (!srcImage.naturalWidth && !srcImage.naturalHeight) { + var _this = this; + srcImage.onload = function() { + var listeners = _this.imageLoadListeners; + if (listeners) { + _this.imageLoadListeners = null; + for (var i=0, len=listeners.length; i maxWidth) { + width = maxWidth; + height = (imgHeight * width / imgWidth) << 0; + } + if (maxHeight && height > maxHeight) { + height = maxHeight; + width = (imgWidth * height / imgHeight) << 0; + } + var opt = { width : width, height : height }; + for (var k in options) opt[k] = options[k]; + + var tagName = target.tagName.toLowerCase(); + if (tagName === 'img') { + target.src = renderImageToDataURL(this.srcImage, opt, doSquash); + } else if (tagName === 'canvas') { + renderImageToCanvas(this.srcImage, target, opt, doSquash); + } + if (typeof this.onrender === 'function') { + this.onrender(target); + } + }; + + /** + * Export class to global + */ + if (typeof define === 'function' && define.amd) { + define([], function() { return MegaPixImage; }); // for AMD loader + } else { + this.MegaPixImage = MegaPixImage; + } + +})();