Re: Visual artifacts in image when writing to disk

• Subject: Re: Visual artifacts in image when writing to disk
• From: Pierre-Olivier Latour <email@hidden>
• Date: Mon, 22 May 2006 10:21:26 -0700
• Delivered-to: email@hidden
• Delivered-to: email@hidden

In the past it has worked fine on my PowerBook G4 without any visual artifacts. However when using a Mac Mini Core Duo, while the image shown on the screen live looks fine, when it is saved to file it suddenly introduces strange visual artifacts (see attached). The problem can be mitigated by increasing the shutter speed of the camera, but I find it strange that the image on screen (on the powerbook and mini) displays none of these artifacts.

Is there a way to fix this problem in software?

Here is the code I am using to write the image to disk:

NSImage * image = [[view valueForOutputKey:@"image"] copy];
NSData *imageData = [image TIFFRepresentation];
NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:imageData];
NSDictionary *imageProps = [NSDictionary dictionaryWithObject: [NSNumber numberWithFloat:0.9] forKey:NSImageCompressionFactor];
imageData = [imageRep representationUsingType:NSJPEGFileType properties:imageProps];
[imageData writeToFile:file atomically:YES];

Does it work if you just do this?

NSData *imageData = [image TIFFRepresentation];
[imageData writeToFile:file atomically:YES];

________________________________________________________
Pierre-Olivier Latour                            	email@hidden
Quartz Composer Team				Apple Computer, Inc.

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