I posted this question at http://stackoverflow.com/questions/1773360/how-to-compress-jpeg-image-with-cocoa . Copy and paste: I have an jpeg image and I want to be able to incrementally compress it using Cocoa/Core Image/Core Graphics. For example, I have A.jpg (3MB), I compress A and get B.jpg (1MB), compress B and get C.jpg (400KB), and so on till the image can't be compressed anymore.
I am trying to use NSBitmapImageRep representationUsingType:properties without much success. I use an image rep created from compressed image data to try and compress further, but this doesn't work well, if I use a compression factor that is the same factor used to create the initial compressed data. Here is the code that I have been wrangling with <code> NSString * fileName = @"largeImage.jpg"; NSLog(@"== Initializing ==\n"); NSData * imageData = [NSData dataWithContentsOfFile:fileName]; NSLog(@"imageData length: %d\n", [imageData length]); NSImage * image = [[NSImage alloc] initWithData:imageData]; NSBitmapImageRep * bitmapRep = [[image representations] objectAtIndex:0]; NSData * data = [bitmapRep representationUsingType:NSJPEGFileType properties:nil]; NSLog(@"data length: %d\n", [data length]); NSDictionary * dict = [NSDictionary dictionaryWithObject: [NSNumber numberWithFloat:0.5] forKey:NSImageCompressionFactor]; NSData * data5 = [bitmapRep representationUsingType:NSJPEGFileType properties:dict]; NSLog(@"data5 length: %d\n", [data5 length]); NSLog(@"== End ==\n\n"); NSLog(@"== Image from Data5 ==\n"); NSImage * imageFromData5 = [[NSImage alloc] initWithData:data5]; NSBitmapImageRep * bitmapRepFromData5 = [[imageFromData5 representations] objectAtIndex:0]; NSData * dataFromImageFromData5 = [bitmapRepFromData5 representationUsingType:NSJPEGFileType properties:nil]; NSLog(@"dataFromImageFromData5 length: %d\n", [dataFromImageFromData5 length]); dict = [NSDictionary dictionaryWithObject: [NSNumber numberWithFloat:0.5] forKey:NSImageCompressionFactor]; NSData * dataFiveFromImageWithData5 = [bitmapRepFromData5 representationUsingType:NSJPEGFileType properties:dict]; NSLog(@"dataFiveFromImageWithData5 length: %d\n", [dataFiveFromImageWithData5 length]); NSLog(@"== End ==\n\n"); </code> This is my result <output> > == Initializing == > imageData length: 1882694 > data length: 1888365 > data5 length: 1102461 > == End == > == Image from Data5 == > dataFromImageFromData5 length: 1646137 > dataFiveFromImageWithData5 length: 1102115 > == End == Try a different image > == Initializing == > imageData length: 3620257 > data length: 2889458 > data5 length: 1404750 > == End == > == Image from Data5 == > dataFromImageFromData5 length: 2007951 > dataFiveFromImageWithData5 length: 1405398 > == End == </output> _______________________________________________ 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
