Be sure to check the endianness of the computer when choosing the
pixel format. The original ImageWriter plugin has this code:
#if __BIG_ENDIAN__
pixelFormat = QCPlugInPixelFormatARGB8;
#else
pixelFormat = QCPlugInPixelFormatBGRA8;
#endif
On Apr 16, 2008, at 2:37 AM, Alex Drinkwater wrote:
Answered my own question!
I just replaced
pixelFormat = QCPlugInPixelFormatARGB8;
with
pixelFormat = QCPlugInPixelFormatBGRA8;
recompiled, and now the plugin works fine!
Apologies for wasting your time, guys,
alx
----- Original Message ----
From: Alex Drinkwater <[EMAIL PROTECTED]>
To: [email protected]
Sent: Wednesday, 16 April, 2008 10:28:40 AM
Subject: Image Writer Plugin
There seems to be an issue with the Image Writer plugin (from the
Developer/Examples/Quartz Composer/Plugins folder) on Intel
machines. I've done some tests, and determined that it's swapping
the RGBA channels of the captured image so that they become GRAB (ie
Red becomes Green, Green becomes Red, Blue becomes Alpha, and the
Alpha is swapped with the Blue channel).
I've tried swizzling the color channels of the image before they go
into the Image Writer plugin, but this doesn't seem to make any
difference to the output, which is odd, because if I pipe the output
of the swizzle CIFilter to a billboard, the channels appear
reordered as I'd expect.
I'm guessing this is some kind of endian-related issue. Anyone know
how this might be fixed?
I've managed to isolate the part of the code in the XCode project
relating to colorspaces, if this helps at all:
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
/* Figure out pixel format and colorspace to use */
colorSpace = [qcImage imageColorSpace];
if(CGColorSpaceGetModel(colorSpace) == kCGColorSpaceModelMonochrome)
pixelFormat = QCPlugInPixelFormatI8;
else if(CGColorSpaceGetModel(colorSpace) == kCGColorSpaceModelRGB)
pixelFormat = QCPlugInPixelFormatARGB8;
else
return NO;
/* Get a buffer representation from the image in its native
colorspace */
if(![qcImage lockBufferRepresentationWithPixelFormat:pixelFormat
colorSpace:colorSpace forBounds:[qcImage imageBounds]])
return NO;
/* Create CGImage from buffer */
dataProvider = CGDataProviderCreateWithData(NULL, [qcImage
bufferBaseAddress], [qcImage bufferPixelsHigh] * [qcImage
bufferBytesPerRow], NULL);
cgImage = CGImageCreate([qcImage bufferPixelsWide], [qcImage
bufferPixelsHigh], 8, (pixelFormat == QCPlugInPixelFormatI8 ? 8 :
32), [qcImage bufferBytesPerRow], colorSpace, (pixelFormat ==
QCPlugInPixelFormatI8 ? 0 : kCGImageAlphaPremultipliedFirst |
kCGBitmapByteOrder32Host), dataProvider, NULL, false,
kCGRenderingIntentDefault);
CGDataProviderRelease(dataProvider);
if(cgImage == NULL) {
[qcImage unlockBufferRepresentation];
return NO;
}
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Cheers,
alx
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