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copied!<p>This seems to work and produce not-all-black output. There may be a way to do it that doesn't involve a manual conversion to grayscale first, but at least it works!</p> <pre><code>static void WriteCCITTTiffWithCGImage_URL_(CGImageRef im, CFURLRef url) { // produce grayscale image CGImageRef grayscaleImage; { CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericGray); CGContextRef bitmapCtx = CGBitmapContextCreate(NULL, CGImageGetWidth(im), CGImageGetHeight(im), 8, 0, colorSpace, kCGImageAlphaNone); CGContextDrawImage(bitmapCtx, CGRectMake(0,0,CGImageGetWidth(im), CGImageGetHeight(im)), im); grayscaleImage = CGBitmapContextCreateImage(bitmapCtx); CFRelease(bitmapCtx); CFRelease(colorSpace); } // generate options for ImageIO. Man this sucks in C. CFMutableDictionaryRef options = CFDictionaryCreateMutable(kCFAllocatorDefault, 2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks); { { CFMutableDictionaryRef tiffOptions = CFDictionaryCreateMutable(kCFAllocatorDefault, 1, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks); int fourInt = 4; CFNumberRef fourNumber = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &fourInt); CFDictionarySetValue(tiffOptions, kCGImagePropertyTIFFCompression, fourNumber); CFRelease(fourNumber); CFDictionarySetValue(options, kCGImagePropertyTIFFDictionary, tiffOptions); CFRelease(tiffOptions); } { int oneInt = 1; CFNumberRef oneNumber = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &oneInt); CFDictionarySetValue(options, kCGImagePropertyDepth, oneNumber); CFRelease(oneNumber); } } // write file CGImageDestinationRef idst = CGImageDestinationCreateWithURL(url, kUTTypeTIFF, 1, NULL); CGImageDestinationAddImage(idst, grayscaleImage, options); CGImageDestinationFinalize(idst); // clean up CFRelease(idst); CFRelease(options); CFRelease(grayscaleImage); } Nepheli:tmp ken$ tiffutil -info /tmp/output.tiff Directory at 0x1200 Image Width: 842 Image Length: 562 Bits/Sample: 1 Sample Format: unsigned integer Compression Scheme: CCITT Group 4 facsimile encoding Photometric Interpretation: "min-is-black" Orientation: row 0 top, col 0 lhs Samples/Pixel: 1 Number of Strips: 1 Planar Configuration: Not planar </code></pre>

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