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    <p>This is possible and I previously tried two paths:</p> <ol> <li><p>Convert to Grayscale then apply pixel by pixel conversion to B&amp;W.<br/> --Problem with this is I don't get good results with images with transparency.</p></li> <li><p>If you're not very strict, given an RGBA image, get the pixel RGB average and convert to B&amp;W with a supplied threshold and retain its transparency. Technically this is still RGBA but more of Black, White and Transparency.</p></li> </ol> <p>e.g.</p> <pre><code> UIImage *originalImage = [UIImage imageNamed:@"option_bluetooth.png"]; unsigned char *pixelBuffer = [self getPixelData:originalImage.CGImage]; size_t length = originalImage.size.width * originalImage.size.height * 4; CGFloat intensity; int bw; //50% threshold const CGFloat THRESHOLD = 0.5; for (int index = 0; index &lt; length; index += 4) { intensity = (pixelBuffer[index] + pixelBuffer[index + 1] + pixelBuffer[index + 2]) / 3. / 255.; if (intensity &gt; THRESHOLD) { bw = 255; } else { bw = 0; } pixelBuffer[index] = bw; pixelBuffer[index + 1] = bw; pixelBuffer[index + 2] = bw; } CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB(); CGContextRef bitmapContext=CGBitmapContextCreate(pixelBuffer, originalImage.size.width, originalImage.size.height, 8, 4*originalImage.size.width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault); CFRelease(colorSpace); free(pixelBuffer); CGImageRef cgImage=CGBitmapContextCreateImage(bitmapContext); CGContextRelease(bitmapContext); UIImage *bwImage = [UIImage imageWithCGImage:cgImage]; </code></pre> <p>I get the pixel data by writing to an offscreen context (the new way of getting the raw data which Apple suggests does not work for me)</p> <p>e.g.</p> <pre><code> CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); unsigned char *rawData = malloc(imageHeight * imageWidth * 4); CGContextRef offscreenContext = CGBitmapContextCreate(rawData, imageWidth, imageHeight, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault); CGColorSpaceRelease(colorSpace); CGContextDrawImage(offscreenContext, CGRectMake(0, 0, imageWidth, imageHeight), cgCropped); CGContextRelease(offscreenContext); </code></pre> <p>Here's the code to get Pixel Data</p> <pre><code>+ (unsigned char *) getPixelData: (CGImageRef) cgCropped { size_t imageWidth = CGImageGetWidth(cgCropped); size_t imageHeight = CGImageGetHeight(cgCropped); size_t bitsPerComponent = 8; size_t bytesPerPixel = 4; size_t bytesPerRow = bytesPerPixel * imageWidth; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); unsigned char *rawData = malloc(imageHeight * imageWidth * 4); CGContextRef offscreenContext = CGBitmapContextCreate(rawData, imageWidth, imageHeight, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault); CGColorSpaceRelease(colorSpace); CGContextDrawImage(offscreenContext, CGRectMake(0, 0, imageWidth, imageHeight), cgCropped); CGContextRelease(offscreenContext); return rawData; } </code></pre>
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    1. POIphone convert color image to 2bit image (black-white)
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    1. COThanks.. Will try this...
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    2. COHi Manny , I tried this answer i am getting error as "use of undeclared identifier GraphicsUtils" What is the necessary packages to import .. Please Guide me .. i need this Thanks in Advance
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    3. COHi, GraphicUtils is a custom utility, it should be easy to get pixel data just search the net for solution.
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