You are right, thanks a lot for shedding the light! -Jane On Sep 11, 2011, at 12:12 PM, Anatoly Geyfman wrote:
> 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] > -- 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]
