[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Is this a bug in Tiger's NSBitmapImageRep?

Subject: Is this a bug in Tiger's NSBitmapImageRep?
From: Marc Liyanage <email@hidden>
Date: Tue, 3 May 2005 00:06:55 +0200
Delivered-to: email@hidden
Delivered-to: email@hidden

I noticed today that a piece of code I wrote for Jaguar/Panther no longer works right in Tiger. I didn't change anything, and the exact same code still works flawlessly on Panther.

I am using the method

initWithBitmapDataPlanes:pixelsWide:pixelsHigh:bitsPerSample:samplesPerP ixel:hasAlpha:isPlanar:colorSpaceName:bytesPerRow:bitsPerPixel:

to create the NSBitmapImageRep, and then I fetch the bitmap base address and fill it with data. On Tiger, the resulting image looks like garbage when displayed or serialized to TIFF. It looks like there's something wrong with the data length calculations, depending on the target width the rows are skewed. It seems to work correctly when the image width in pixels is a multiple of 24 which is the number of bits per sample times the number of channels.

The test case below produces correct results on Panther, and the exact same binary run on Tiger will show the problem. For comparison, the ".raw" file can be opened in Photoshop.

Is this a bug in Tiger or have I been doing something wrong all along without getting into trouble?

I see there's a new, similar method in Tiger but I'd rather not use that one because my code needs to run on Jaguar and Panther too.

#import <Cocoa/Cocoa.h>

int main (int argc, const char * argv[]) {

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    int width = 100, height = 100;
    int datalength = width * height * 3;

NSBitmapImageRep *imageRep = [[[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:width pixelsHigh:height bitsPerSample:8 samplesPerPixel:3 hasAlpha:NO isPlanar:NO colorSpaceName:NSDeviceRGBColorSpace bytesPerRow:0 bitsPerPixel:0] autorelease];

    char *destbuffer = [imageRep bitmapData];

    unsigned char c = 0;
    char *p = destbuffer;
    while (p < destbuffer + datalength) {
        *p++ = c;
        *p++ = c;
        *p++ = c;
        c++;
    }

[[NSData dataWithBytes:destbuffer length:datalength] writeToFile:@"/tmp/out_pixels.raw" atomically:YES];

NSImage *image = [[NSImage alloc] initWithSize:NSMakeSize(0.0, 0.0)]; [image addRepresentation:imageRep];

[[image TIFFRepresentation] writeToFile:@"/tmp/out_pixels.tiff" atomically:YES];

    [pool release];
    return 0;
}


_________________________________________________________________
Marc Liyanage                               http://www.entropy.ch


_______________________________________________
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/email@hidden

This email sent to email@hidden

Follow-Ups:
- Re: Is this a bug in Tiger's NSBitmapImageRep?
  - From: Andrew Platzer <email@hidden>

Prev by Date: Re: (freely) Rotating Text
Next by Date: Re: When is (NSColor) black not black?
Previous by thread: Re: Spotlight -- Metadata importer vs file package containing rtfd files
Next by thread: Re: Is this a bug in Tiger's NSBitmapImageRep?
Index(es):
- Date
- Thread

Home