1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 | /* * Canvas2Image v0.1 * Copyright (c) 2008 Jacob Seidelin, cupboy@gmail.com * MIT License [http://www.opensource.org/licenses/mit-license.php] */ var Canvas2Image = (function() { // check if we have canvas support var oCanvas = document.createElement("canvas"), sc = String.fromCharCode, strDownloadMime = "image/octet-stream", bReplaceDownloadMime = false; // no canvas, bail out. if (!oCanvas.getContext) { return { saveAsBMP : function(){}, saveAsPNG : function(){}, saveAsJPEG : function(){} } } var bHasImageData = !!(oCanvas.getContext("2d").getImageData), bHasDataURL = !!(oCanvas.toDataURL), bHasBase64 = !!(window.btoa); // ok, we're good var readCanvasData = function(oCanvas) { var iWidth = parseInt(oCanvas.width), iHeight = parseInt(oCanvas.height); return oCanvas.getContext("2d").getImageData(0,0,iWidth,iHeight); } // base64 encodes either a string or an array of charcodes var encodeData = function(data) { var i, aData, strData = ""; if (typeof data == "string") { strData = data; } else { aData = data; for (i = 0; i < aData.length; i++) { strData += sc(aData[i]); } } return btoa(strData); } // creates a base64 encoded string containing BMP data takes an imagedata object as argument var createBMP = function(oData) { var strHeader = '', iWidth = oData.width, iHeight = oData.height; strHeader += 'BM'; var iFileSize = iWidth*iHeight*4 + 54; // total header size = 54 bytes strHeader += sc(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); strHeader += sc(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); strHeader += sc(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); strHeader += sc(iFileSize % 256); strHeader += sc(0, 0, 0, 0, 54, 0, 0, 0); // data offset strHeader += sc(40, 0, 0, 0); // info header size var iImageWidth = iWidth; strHeader += sc(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); strHeader += sc(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); strHeader += sc(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); strHeader += sc(iImageWidth % 256); var iImageHeight = iHeight; strHeader += sc(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); strHeader += sc(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); strHeader += sc(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); strHeader += sc(iImageHeight % 256); strHeader += sc(1, 0, 32, 0); // num of planes & num of bits per pixel strHeader += sc(0, 0, 0, 0); // compression = none var iDataSize = iWidth*iHeight*4; strHeader += sc(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); strHeader += sc(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); strHeader += sc(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); strHeader += sc(iDataSize % 256); strHeader += sc(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0); // these bytes are not used var aImgData = oData.data, strPixelData = "", c, x, y = iHeight, iOffsetX, iOffsetY, strPixelRow; do { iOffsetY = iWidth*(y-1)*4; strPixelRow = ""; for (x = 0; x < iWidth; x++) { iOffsetX = 4*x; strPixelRow += sc( aImgData[iOffsetY + iOffsetX + 2], // B aImgData[iOffsetY + iOffsetX + 1], // G aImgData[iOffsetY + iOffsetX], // R aImgData[iOffsetY + iOffsetX + 3] // A ); } strPixelData += strPixelRow; } while (--y); return encodeData(strHeader + strPixelData); } // sends the generated file to the client var saveFile = function(strData) { if (!window.open(strData)) { document.location.href = strData; } } var makeDataURI = function(strData, strMime) { return "data:" + strMime + ";base64," + strData; } // generates a <img> object containing the imagedata var makeImageObject = function(strSource) { var oImgElement = document.createElement("img"); oImgElement.src = strSource; return oImgElement; } var scaleCanvas = function(oCanvas, iWidth, iHeight) { if (iWidth && iHeight) { var oSaveCanvas = document.createElement("canvas"); oSaveCanvas.width = iWidth; oSaveCanvas.height = iHeight; oSaveCanvas.style.width = iWidth+"px"; oSaveCanvas.style.height = iHeight+"px"; var oSaveCtx = oSaveCanvas.getContext("2d"); oSaveCtx.drawImage(oCanvas, 0, 0, oCanvas.width, oCanvas.height, 0, 0, iWidth, iWidth); return oSaveCanvas; } return oCanvas; } return { saveAsPNG : function(oCanvas, bReturnImg, iWidth, iHeight) { if (!bHasDataURL) return false; var oScaledCanvas = scaleCanvas(oCanvas, iWidth, iHeight), strMime = "image/png", strData = oScaledCanvas.toDataURL(strMime); if (bReturnImg) { return makeImageObject(strData); } else { saveFile(bReplaceDownloadMime ? strData.replace(strMime, strDownloadMime) : strData); } return true; }, saveAsJPEG : function(oCanvas, bReturnImg, iWidth, iHeight) { if (!bHasDataURL) return false; var oScaledCanvas = scaleCanvas(oCanvas, iWidth, iHeight), strMime = "image/jpeg", strData = oScaledCanvas.toDataURL(strMime); // check if browser actually supports jpeg by looking for the mime type in the data uri. if not, return false if (strData.indexOf(strMime) != 5) return false; if (bReturnImg) { return makeImageObject(strData); } else { saveFile(bReplaceDownloadMime ? strData.replace(strMime, strDownloadMime) : strData); } return true; }, saveAsBMP : function(oCanvas, bReturnImg, iWidth, iHeight) { if (!(bHasDataURL && bHasImageData && bHasBase64)) return false; var oScaledCanvas = scaleCanvas(oCanvas, iWidth, iHeight), strMime = "image/bmp", oData = readCanvasData(oScaledCanvas), strImgData = createBMP(oData); if (bReturnImg) { return makeImageObject(makeDataURI(strImgData, strMime)); } else { saveFile(makeDataURI(strImgData, strMime)); } return true; } }; })(); |