Question

I have a bit of a weird problem. I create a UIImage with imageNamed extract colour data from it and then set it to another class.

Then from that class when I do a drawRect I get an EXC_BAD_ACCESS when doing the drawRect.

Here is where I load the image:

UIImage*    pImageHM    = [UIImage imageNamed:@"Heatmap2.png"];
CGImageRef  irHM        = [pImageHM CGImage];
CFDataRef   drHM        = CGDataProviderCopyData( CGImageGetDataProvider( irHM ) );
R8G8B8A8*   pDataHM     = (R8G8B8A8*)CFDataGetBytePtr( drHM );

unsigned int colour     = 0;
unsigned int colourMax  = 256;
while( colour < colourMax )
{
    // Extract image data.
    colour++;
}
[mpView SetScale: pImageHM];

CFRelease( drHM );
CGImageRelease( irHM );

The SetScale function is defined as follows:

- (void) SetScale: (UIImage*)pImage
{
    [mpScale release];

    mpScale = pImage;

    [mpScale retain];

    [self setNeedsDisplay];
}

And finally I render it as follows:

    CGContextRotateCTM( ctx, -M_PI_2 );
    CGContextTranslateCTM( ctx, -(rect.size.height - 48), 0);

    [mpScale drawInRect: CGRectMake( 0,                    rect.size.width - 16,
                                    rect.size.height - 48, 16 )];

    CGContextTranslateCTM( ctx, (rect.size.height - 48), 0 );
    CGContextRotateCTM( ctx, M_PI_2 );

Why would the mpScale raise an EXC_BAD_ACCESS? Given the UIImage has been retained the fact it was subsequently autoreleased after I had called SetScale should be neither here nor there.

I should add that if I don’t call SetScale (such that mpScale remains as nil) then I get no crash and, obviously, I don’t see anything where the scale ought to be.

Thanks in advance!

Answer 1

CGImageRef irHM = [pImageHM CGImage];

You do not own this CGImage, but you are releasing it.

CGImageRelease( irHM );