capture is a CGImageRef returned from a call to CGWindowListCreateImage(). When I try to turn it into an NSImage directly it mysteriously doubles in size. If I manually create a an NSBitmapImageRep from capture and then add it to an empty NSImage everything works ok.
My hardware setup is a retina MBP + non-retina external display. The capture is taking place on the non-retina screen.
NSLog(@"capture image size: %d %d", CGImageGetWidth(capture), CGImageGetHeight(capture));
NSLog(@"logical image size: %f %f", viewRect.size.width, viewRect.size.height);
NSBitmapImageRep *debugRep;
NSImage *image;
//
// Create NSImage directly
image = [[NSImage alloc] initWithCGImage:capture size:NSSizeFromCGSize(viewRect.size)];
debugRep = [[image representations] objectAtIndex:0];
NSLog(@"pixel size, NSImage direct: %d %d", debugRep.pixelsWide, debugRep.pixelsHigh);
//
// Create representation manually
NSBitmapImageRep *imageRep = [[NSBitmapImageRep alloc] initWithCGImage:capture];
image = [[NSImage alloc] initWithSize:NSSizeFromCGSize(viewRect.size)];
[image addRepresentation:imageRep];
[imageRep release];
debugRep = [[image representations] objectAtIndex:0];
NSLog(@"pixel size, NSImage + manual representation: %d %d", debugRep.pixelsWide, debugRep.pixelsHigh);Log output:
capture image size: 356 262
logical image size: 356.000000 262.000000
pixel size, NSImage direct: 712 524
pixel size, NSImage + manual representation: 356 262
Why is this happening?