are you running this via the file system or through a server? The DOM Exception you see is most likely because you cannot do CANVAS manipulation without accessing the file through an http server.
-- Anatoly Geyfman http://www.geyfman.net On Sunday, September 11, 2011 at 9:17 AM, Jane wrote: > Hi, I am a newbie on JS and was trying to do alpha blending without a > full success for a couple of days. The code is here: > > var img1 = document.getElementById('foreground'); > var img2 = document.getElementById('background'); > var canvas = document.getElementById("result"); > var context = canvas.getContext("2d"); > var width = img1.width; > var height = img1.height; > canvas.width = width; > canvas.height = height; > var alpha = 0.5; > var pixels = 4 * width * height; > // get foreground image data > context.drawImage(img1, 0, 0); > var image1 = context.getImageData(0, 0, width, height); > var imageData1 = image1.data; > // get background image data > context.drawImage(img2, 0, 0); > var image2 = context.getImageData(0, 0, width, height); > var imageData2 = image2.data; > // alpha blending > while (pixels--) { > imageData1[pixels] = imageData1[pixels] * alpha + > imageData2[pixels] * alpha; > } > // send the result to canvas > image1.data = imageData1; > context.putImageData(image1, 0, 0); > > > I found that Safari displays blended image just fine. However in > Chrome, the line on context.getImageData triggered the following error > message: > > 58 Uncaught Error: SECURITY_ERR: DOM Exception 18 > > Thank you very much in advance, > > Jane > > -- > To view archived discussions from the original JSMentors Mailman list: > http://www.mail-archive.com/[email protected]/ > > To search via a non-Google archive, visit here: > http://www.mail-archive.com/[email protected]/ > > To unsubscribe from this group, send email to > [email protected] > (mailto:[email protected]) -- To view archived discussions from the original JSMentors Mailman list: http://www.mail-archive.com/[email protected]/ To search via a non-Google archive, visit here: http://www.mail-archive.com/[email protected]/ To unsubscribe from this group, send email to [email protected]
