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Determine if a UIImage is generally dark or generally light
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| BOOL isDarkImage(UIImage* inputImage){ | |
| BOOL isDark = FALSE; | |
| CFDataRef imageData = CGDataProviderCopyData(CGImageGetDataProvider(inputImage.CGImage)); | |
| const UInt8 *pixels = CFDataGetBytePtr(imageData); | |
| int darkPixels = 0; | |
| int length = CFDataGetLength(imageData); | |
| int const darkPixelThreshold = (inputImage.size.width*inputImage.size.height)*.45; | |
| for(int i=0; i<length; i+=4) | |
| { | |
| int r = pixels[i]; | |
| int g = pixels[i+1]; | |
| int b = pixels[i+2]; | |
| //luminance calculation gives more weight to r and b for human eyes | |
| float luminance = (0.299*r + 0.587*g + 0.114*b); | |
| if (luminance<150) darkPixels ++; | |
| } | |
| if (darkPixels >= darkPixelThreshold) | |
| isDark = YES; | |
| CFRelease(imageData); | |
| return isDark; | |
| } |
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