Add backload

2016-11-17 15:02:29 -05:00
parent eeacfebec9
commit a3b8b7a881
263 changed files with 29788 additions and 18 deletions
@@ -0,0 +1,181 @@
+/*
+ * JavaScript Load Image iOS scaling fixes 1.0.3
+ * https://github.com/blueimp/JavaScript-Load-Image
+ *
+ * Copyright 2013, Sebastian Tschan
+ * https://blueimp.net
+ *
+ * iOS image scaling fixes based on
+ * https://github.com/stomita/ios-imagefile-megapixel
+ *
+ * Licensed under the MIT license:
+ * http://www.opensource.org/licenses/MIT
+ */
+
+/*jslint nomen: true, bitwise: true */
+/*global define, window, document */
+
+(function (factory) {
+    'use strict';
+    if (typeof define === 'function' && define.amd) {
+        // Register as an anonymous AMD module:
+        define(['load-image'], factory);
+    } else {
+        // Browser globals:
+        factory(window.loadImage);
+    }
+}(function (loadImage) {
+    'use strict';
+
+    // Only apply fixes on the iOS platform:
+    if (!window.navigator || !window.navigator.platform ||
+             !(/iP(hone|od|ad)/).test(window.navigator.platform)) {
+        return;
+    }
+
+    var originalRenderMethod = loadImage.renderImageToCanvas;
+
+    // Detects subsampling in JPEG images:
+    loadImage.detectSubsampling = function (img) {
+        var canvas,
+            context;
+        if (img.width * img.height > 1024 * 1024) { // only consider mexapixel images
+            canvas = document.createElement('canvas');
+            canvas.width = canvas.height = 1;
+            context = canvas.getContext('2d');
+            context.drawImage(img, -img.width + 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 context.getImageData(0, 0, 1, 1).data[3] === 0;
+        }
+        return false;
+    };
+
+    // Detects vertical squash in JPEG images:
+    loadImage.detectVerticalSquash = function (img, subsampled) {
+        var naturalHeight = img.naturalHeight || img.height,
+            canvas = document.createElement('canvas'),
+            context = canvas.getContext('2d'),
+            data,
+            sy,
+            ey,
+            py,
+            alpha;
+        if (subsampled) {
+            naturalHeight /= 2;
+        }
+        canvas.width = 1;
+        canvas.height = naturalHeight;
+        context.drawImage(img, 0, 0);
+        data = context.getImageData(0, 0, 1, naturalHeight).data;
+        // search image edge pixel position in case it is squashed vertically:
+        sy = 0;
+        ey = naturalHeight;
+        py = naturalHeight;
+        while (py > sy) {
+            alpha = data[(py - 1) * 4 + 3];
+            if (alpha === 0) {
+                ey = py;
+            } else {
+                sy = py;
+            }
+            py = (ey + sy) >> 1;
+        }
+        return (py / naturalHeight) || 1;
+    };
+
+    // Renders image to canvas while working around iOS image scaling bugs:
+    // https://github.com/blueimp/JavaScript-Load-Image/issues/13
+    loadImage.renderImageToCanvas = function (
+        canvas,
+        img,
+        sourceX,
+        sourceY,
+        sourceWidth,
+        sourceHeight,
+        destX,
+        destY,
+        destWidth,
+        destHeight
+    ) {
+        if (img._type === 'image/jpeg') {
+            var context = canvas.getContext('2d'),
+                tmpCanvas = document.createElement('canvas'),
+                tileSize = 1024,
+                tmpContext = tmpCanvas.getContext('2d'),
+                subsampled,
+                vertSquashRatio,
+                tileX,
+                tileY;
+            tmpCanvas.width = tileSize;
+            tmpCanvas.height = tileSize;
+            context.save();
+            subsampled = loadImage.detectSubsampling(img);
+            if (subsampled) {
+                sourceX /= 2;
+                sourceY /= 2;
+                sourceWidth /= 2;
+                sourceHeight /= 2;
+            }
+            vertSquashRatio = loadImage.detectVerticalSquash(img, subsampled);
+            if (subsampled || vertSquashRatio !== 1) {
+                sourceY *= vertSquashRatio;
+                destWidth = Math.ceil(tileSize * destWidth / sourceWidth);
+                destHeight = Math.ceil(
+                    tileSize * destHeight / sourceHeight / vertSquashRatio
+                );
+                destY = 0;
+                tileY = 0;
+                while (tileY < sourceHeight) {
+                    destX = 0;
+                    tileX = 0;
+                    while (tileX < sourceWidth) {
+                        tmpContext.clearRect(0, 0, tileSize, tileSize);
+                        tmpContext.drawImage(
+                            img,
+                            sourceX,
+                            sourceY,
+                            sourceWidth,
+                            sourceHeight,
+                            -tileX,
+                            -tileY,
+                            sourceWidth,
+                            sourceHeight
+                        );
+                        context.drawImage(
+                            tmpCanvas,
+                            0,
+                            0,
+                            tileSize,
+                            tileSize,
+                            destX,
+                            destY,
+                            destWidth,
+                            destHeight
+                        );
+                        tileX += tileSize;
+                        destX += destWidth;
+                    }
+                    tileY += tileSize;
+                    destY += destHeight;
+                }
+                context.restore();
+                return canvas;
+            }
+        }
+        return originalRenderMethod(
+            canvas,
+            img,
+            sourceX,
+            sourceY,
+            sourceWidth,
+            sourceHeight,
+            destX,
+            destY,
+            destWidth,
+            destHeight
+        );
+    };
+
+}));