/* eslint-disable */
/**
* 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 <shinichi.tomita@gmail.com>
* Released under the MIT license
*/
/**
* 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;
if (!(iw + ih)) return;
var width = options.width,
height = options.height;
var ctx = canvas.getContext('2d');
ctx.save();
transformCoordinate(canvas, ctx, 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, ctx, 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;
}
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;
}
}
var URL =
window.URL && window.URL.createObjectURL
? window.URL
: window.webkitURL && window.webkitURL.createObjectURL
? window.webkitURL
: null;
/**
* MegaPixImage class
*/
function MegaPixImage(srcImage) {
if (window.Blob && srcImage instanceof Blob) {
if (!URL) {
throw Error('No createObjectURL function found to create blob url');
}
var img = new Image();
img.src = URL.createObjectURL(srcImage);
this.blob = srcImage;
srcImage = img;
}
if (!srcImage.naturalWidth && !srcImage.naturalHeight) {
var _this = this;
srcImage.onload = srcImage.onerror = function() {
var listeners = _this.imageLoadListeners;
if (listeners) {
_this.imageLoadListeners = null;
for (var i = 0, len = listeners.length; i < len; i++) {
listeners[i]();
}
}
};
this.imageLoadListeners = [];
}
this.srcImage = srcImage;
}
/**
* Rendering megapix image into specified target element
*/
MegaPixImage.prototype.render = function(target, options, callback) {
if (this.imageLoadListeners) {
var _this = this;
this.imageLoadListeners.push(function() {
_this.render(target, options, callback);
});
return;
}
options = options || {};
var imgWidth = this.srcImage.naturalWidth,
imgHeight = this.srcImage.naturalHeight,
width = options.width,
height = options.height,
maxWidth = options.maxWidth,
maxHeight = options.maxHeight,
doSquash = !this.blob || this.blob.type === 'image/jpeg';
if (width && !height) {
height = ((imgHeight * width) / imgWidth) << 0;
} else if (height && !width) {
width = ((imgWidth * height) / imgHeight) << 0;
} else {
width = imgWidth;
height = imgHeight;
}
if (maxWidth && width > 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);
}
if (callback) {
callback();
}
if (this.blob) {
this.blob = null;
URL.revokeObjectURL(this.srcImage.src);
}
};
export default MegaPixImage;