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@justinHowlett
Last active July 9, 2024 11:53
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Determine if a UIImage is generally dark or generally light
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;
}
@adamcichy
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I have created Swift categories for UIImage and CGImage based on this method. For anyone who is interested: ImageDarkness.swift

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