Thanks a lot for this code Rob!
Quick question (2 actually), right now Im drawing my CIImage in a
custom view... would drawing the CIImage in my view's drawRect method
achieve the same (leak-free) result as your piece of code??? i.e.
something simple like:
// previewImage is an NSBitmapImageRep that exists already..
- (void)drawRect:(NSRect)rect {
CIImage *outputImage = [[CIImage alloc] initWithData:[previewImage
TIFFRepresentation]];
[outputImage drawInRect: NSMakeRect(0, 0, [previewImage pixelsWide],
[previewImage pixelsHigh])
fromRect:NSMakeRect(0, 0, [previewImage pixelsWide],
[previewImage pixelsHigh])
operation:NSCompositeSourceOver
fraction:1.0];
[outputImage release];
}
Second question; my app does batch image processing so eventually I
will have to draw those CIImage offscreen.. (only for the Color
Control Filter actually)... I assume I have to live with the leak??
J-N
On 3-Dec-08, at 3:10 AM, Rob Keniger wrote:
On 03/12/2008, at 5:34 PM, Jean-Nicolas Jolivet wrote:
Hmm I just found an older post that mentions a big memory leak
problem when drawing CIImage offscreen.... I guess I'll have to do
this differently...
Ah, you've just reminded me. There is a major leak in drawing
CIImage offscreen but you can work around it by rendering to a
CGImageRef in the context of the current window.
Here's the code:
//theImage is an existing NSImage
CIImage *outputImage = [CIImage imageWithData:[theImage
TIFFRepresentation]];
//to draw the image processed by Core Image, we need to draw into
an on-screen graphics context
//this works around a bug in CIImage where drawing in off-screen
graphics contexts causes a huge memory leak
//get the current window's graphics context so that we have an on-
screen context
//usually we would use any view's window but generically you can
just ask for the main window
CIContext *ciContext = [[[NSApp mainWindow] graphicsContext]
CIContext];
if(ciContext == nil)
{
NSLog(@"The CIContext of the main window could not be accessed.
Bailing out of the image creation process.");
return;
}
CGAffineTransform transform;
transform = CGAffineTransformMakeTranslation(0.0,[outputImage
extent].size.height);
transform = CGAffineTransformScale(transform, 1.0, -1.0);
outputImage = [outputImage imageByApplyingTransform:transform];
//render the CIIimage into a CGImageRef in the on-screen context
CGImageRef cgImage = [ciContext createCGImage:outputImage fromRect:
[outputImage extent]];
// Draw the CGImageRef into the current context
if (cgImage != NULL)
{
CGContextDrawImage ([[NSGraphicsContext currentContext]
graphicsPort], [outputImage extent], cgImage);
CGImageRelease (cgImage);
}
--
Rob Keniger
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