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POConvert image to grayscale
 

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    <p>I am trying to convert an image into grayscale in the following way:</p> <pre><code>#define bytesPerPixel 4 #define bitsPerComponent 8 -(unsigned char*) getBytesForImage: (UIImage*)pImage { CGImageRef image = [pImage CGImage]; NSUInteger width = CGImageGetWidth(image); NSUInteger height = CGImageGetHeight(image); NSUInteger bytesPerRow = bytesPerPixel * width; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); unsigned char *rawData = malloc(height * width * 4); CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); CGColorSpaceRelease(colorSpace); CGContextDrawImage(context, CGRectMake(0, 0, width, height), image); CGContextRelease(context); return rawData; } -(UIImage*) processImage: (UIImage*)pImage { DebugLog(@"processing image"); unsigned char *rawData = [self getBytesForImage: pImage]; NSUInteger width = pImage.size.width; NSUInteger height = pImage.size.height; DebugLog(@"width: %d", width); DebugLog(@"height: %d", height); NSUInteger bytesPerRow = bytesPerPixel * width; for (int xCoordinate = 0; xCoordinate &lt; width; xCoordinate++) { for (int yCoordinate = 0; yCoordinate &lt; height; yCoordinate++) { int byteIndex = (bytesPerRow * yCoordinate) + xCoordinate * bytesPerPixel; //Getting original colors float red = ( rawData[byteIndex] / 255.f ); float green = ( rawData[byteIndex + 1] / 255.f ); float blue = ( rawData[byteIndex + 2] / 255.f ); //Processing pixel data float averageColor = (red + green + blue) / 3.0f; red = averageColor; green = averageColor; blue = averageColor; //Assigning new color components rawData[byteIndex] = (unsigned char) red * 255; rawData[byteIndex + 1] = (unsigned char) green * 255; rawData[byteIndex + 2] = (unsigned char) blue * 255; } } NSData* newPixelData = [NSData dataWithBytes: rawData length: height * width * 4]; UIImage* newImage = [UIImage imageWithData: newPixelData]; free(rawData); DebugLog(@"image processed"); return newImage; } </code></pre> <p>So when I want to convert an image I just call processImage:</p> <pre><code>imageToDisplay.image = [self processImage: image]; </code></pre> <p>But imageToDisplay doesn't display. What may be the problem?</p> <p>Thanks.</p>
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