I've been struggling with this issue for a long time, and have not found any working/good example on the net or in any chat..
What I REALLY want to achieve (this can be poor performance): take a JPG (or PNG is great too) file on disk, result with a float *bytes; array holding the floating point precision data from the JPG as R G B A format. Anything that achieves that is a solution here - my current route is to use CIImage just because loading up JPG is so easy with it. What I've been trying: Get the image in to CIImage because it's so convenient.. creating a CGContext, because I should be able to pull the bytes from a CGContext easily since I define data for it, then trying to draw the CIImage in to it. Here's my example code (uninterested in memory leaks at this point): // successfully gets my image CIImage *image = [CIImage alloc initWithContentsOfURL:NSURL fileURLWithPath:in_jpg1]; // I'm working with 512 x 512 exclusively at the moment, I can fix this later NSUInteger width = 512; NSUInteger height = 512; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); // this is the data where I want my bytes to reside at the end. I create the CGContext with it // * 16 because *4bytes per component, *4 components rgba float *rawData = malloc(height * width * 16); // same as what I said above really NSUInteger bytesPerPixel = 16; NSUInteger bytesPerRow = bytesPerPixel * width; NSUInteger bitsPerComponent = 32; // create a CG context, using my float array to hold it's data. Therefore, IF I draw to it // correctly, I should get rawData filled with the bitmap float data of my CIImage CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGBitmapFloatComponents); CGColorSpaceRelease(colorSpace); // draw the CIImage to the 'context'... this is probably the line that's wrong [image drawInRect:NSMakeRect(0, 0, width, height) fromRect:[self bounds] operation:NSCompositeSourceIn fraction 1.0]; The result of this code, if I watch rawData in a memory dump, is that I malloc the array and it becomes all 0's. At no point after that do any of the bytes become non-zero.. the JPG is a red to white gradient so I would of course expect to see components ranging from like ffffffff 0 0 ffffffff, to ffffffff ffffffff fffffff ffffffff Any help is greatly appreciated. This seems to be a huge stumbling block for people.. Robert_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
