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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 | /* * 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"); // no canvas, bail out. if (!oCanvas.getContext) { return { saveAsBMP : function(){}, saveAsPNG : function(){}, saveAsJPEG : function(){} } } var bHasImageData = !!(oCanvas.getContext("2d").getImageData); var bHasDataURL = !!(oCanvas.toDataURL); var bHasBase64 = !!(window.btoa); var strDownloadMime = "image/octet-stream"; // ok, we're good var readCanvasData = function(oCanvas) { var iWidth = parseInt(oCanvas.width); var 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 strData = ""; if (typeof data == "string") { strData = data; } else { var aData = data; for (var i = 0; i < aData.length; i++) { strData += String.fromCharCode(aData[i]); } } return btoa(strData); } // creates a base64 encoded string containing BMP data // takes an imagedata object as argument var createBMP = function(oData) { var aHeader = []; var iWidth = oData.width; var iHeight = oData.height; aHeader.push(0x42); // magic 1 aHeader.push(0x4D); var iFileSize = iWidth*iHeight*3 + 54; // total header size = 54 bytes aHeader.push(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); aHeader.push(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); aHeader.push(iFileSize % 256); iFileSize = Math.floor(iFileSize / 256); aHeader.push(iFileSize % 256); aHeader.push(0); // reserved aHeader.push(0); aHeader.push(0); // reserved aHeader.push(0); aHeader.push(54); // data offset aHeader.push(0); aHeader.push(0); aHeader.push(0); var aInfoHeader = []; aInfoHeader.push(40); // info header size aInfoHeader.push(0); aInfoHeader.push(0); aInfoHeader.push(0); var iImageWidth = iWidth; aInfoHeader.push(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); aInfoHeader.push(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); aInfoHeader.push(iImageWidth % 256); iImageWidth = Math.floor(iImageWidth / 256); aInfoHeader.push(iImageWidth % 256); var iImageHeight = iHeight; aInfoHeader.push(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); aInfoHeader.push(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); aInfoHeader.push(iImageHeight % 256); iImageHeight = Math.floor(iImageHeight / 256); aInfoHeader.push(iImageHeight % 256); aInfoHeader.push(1); // num of planes aInfoHeader.push(0); aInfoHeader.push(24); // num of bits per pixel aInfoHeader.push(0); aInfoHeader.push(0); // compression = none aInfoHeader.push(0); aInfoHeader.push(0); aInfoHeader.push(0); var iDataSize = iWidth*iHeight*3; aInfoHeader.push(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); aInfoHeader.push(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); aInfoHeader.push(iDataSize % 256); iDataSize = Math.floor(iDataSize / 256); aInfoHeader.push(iDataSize % 256); for (var i = 0; i < 16; i++) { aInfoHeader.push(0); // these bytes not used } var iPadding = (4 - ((iWidth * 3) % 4)) % 4; var aImgData = oData.data; var strPixelData = ""; var y = iHeight; do { var iOffsetY = iWidth*(y-1)*4; var strPixelRow = ""; for (var x=0;x<iWidth;x++) { var iOffsetX = 4*x; strPixelRow += String.fromCharCode(aImgData[iOffsetY+iOffsetX+2]); strPixelRow += String.fromCharCode(aImgData[iOffsetY+iOffsetX+1]); strPixelRow += String.fromCharCode(aImgData[iOffsetY+iOffsetX]); } for (var c=0;c<iPadding;c++) { strPixelRow += String.fromCharCode(0); } strPixelData += strPixelRow; } while (--y); return encodeData(aHeader.concat(aInfoHeader)) + encodeData(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); var strData = oScaledCanvas.toDataURL("image/png"); if (bReturnImg) { return makeImageObject(strData); } else { saveFile(strData.replace("image/png", strDownloadMime)); } return true; }, saveAsJPEG : function(oCanvas, bReturnImg, iWidth, iHeight) { if (!bHasDataURL) { return false; } var oScaledCanvas = scaleCanvas(oCanvas, iWidth, iHeight); var strMime = "image/jpeg"; var 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(strData.replace(strMime, strDownloadMime)); } return true; }, saveAsBMP : function(oCanvas, bReturnImg, iWidth, iHeight) { if (!(bHasImageData && bHasBase64)) { return false; } var oScaledCanvas = scaleCanvas(oCanvas, iWidth, iHeight); var oData = readCanvasData(oScaledCanvas); var strImgData = createBMP(oData); if (bReturnImg) { return makeImageObject(makeDataURI(strImgData, "image/bmp")); } else { saveFile(makeDataURI(strImgData, strDownloadMime)); } return true; } }; })(); |