How to draw a NSCIImageRep to an NSView

Question

I am having trouble at drawing a NSCIImageRep which I obtain via a QTKit mCaptureDecompressedVideoOutput.

As I do not want to draw the image using OpenGL, I attempted to subclass a NSView and draw the image there:

- (void) drawRect:(NSRect)dirtyRect
{
    NSLog(@"DrawInRect");
    CGContextRef myContext = [[NSGraphicsContext currentContext] graphicsPort];

    if (imageRep != nil)
    {
       CGImageRef image = [imageRep CGImageForProposedRect: &dirtyRect context:    [NSGraphicsContext currentContext] hints:nil];
       CGContextDrawImage(myContext, dirtyRect, image);
       CGImageRelease(image);
    }  
}

imageRep is a pointer to the CGImageRef I obtain via the mCaptureDecompressedVideoOutput callback

- (void)captureOutput:(QTCaptureOutput *)captureOutput didOutputVideoFrame:(CVImageBufferRef)videoFrame withSampleBuffer:(QTSampleBuffer *)sampleBuffer fromConnection:(QTCaptureConnection *)connection`.

This code crashes my machine. Any suggestions?

Can you post the stack trace from the crash? – Rob Keniger Jan 27 '12 at 13:11 — Rob Keniger, Jan 27 '12 at 13:11

score 4 · Accepted Answer · answered Jan 27 '12 at 21:19

4

You don't need to go via CGImageRef just to draw an NSCIImageRep. Just ask it for a CIImage and draw that:

CIImage* anImage = [yourNSCIImageRep CIImage];
[anImage drawAtPoint:NSZeroPoint
            fromRect:NSRectFromCGRect([anImage extent])
           operation:NSCompositeSourceOver
            fraction:1.0];

answered Jan 27 '12 at 21:19

Rob Keniger

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Yes this is what I found out eventually. I did actually also try converting it to an NSImage, but that led to some unexplicable memory leaks when drawing. – Koffiman Jan 27 '12 at 21:52

How to draw a NSCIImageRep to an NSView

1 Answers1