Question

I need to change the white skin face to dark skin face…
For example American white face to African face(i.e color tone)…

I pick the color value of the pixel by digital color meter it gives the RGB value[red=101,green=63 and blue=43] for dark skin and for white skin it gives the RGB value as [red=253,green=210 and blue=176]…

Then i am setting that value in my code it gives the false result…

Here is my code…

   -(UIImage*)customBlackFilterOriginal
{
    CGImageRef imgSource=self.duplicateImage.image.CGImage;
    CFDataRef m_DataRef1 = CGDataProviderCopyData(CGImageGetDataProvider(imgSource)); 
    UInt8 *dataOriginal=(UInt8 *)CFDataGetBytePtr(m_DataRef1);
    double lengthSource=CFDataGetLength(m_DataRef1);
    NSLog(@"length::%f",lengthSource);
    int redPixel;
    int greenPixel;
    int bluePixel;

    for(int index=0;index<lengthSource;index+=4)
    {

        dataOriginal[index]=dataOriginal[index];
        dataOriginal[index+1]= 101;
        dataOriginal[index+2]= 63;
        dataOriginal[index+3]=43;      

    } 

    NSUInteger width =CGImageGetWidth(imgSource);
    size_t height=CGImageGetHeight(imgSource);
    size_t bitsPerComponent=CGImageGetBitsPerComponent(imgSource);
    size_t bitsPerPixel=CGImageGetBitsPerPixel(imgSource);
    size_t bytesPerRow=CGImageGetBytesPerRow(imgSource);

    NSLog(@"the w:%u H:%lu",width,height);

    CGColorSpaceRef colorspace=CGImageGetColorSpace(imgSource);
    CGBitmapInfo bitmapInfo=CGImageGetBitmapInfo(imgSource);
    CFDataRef newData=CFDataCreate(NULL,dataOriginal,lengthSource);
    CGDataProviderRef provider=CGDataProviderCreateWithCFData(newData);
    CGImageRef newImg=CGImageCreate(width,height,bitsPerComponent,bitsPerPixel,bytesPerRow,colorspace,bitmapInfo,provider,NULL,true,kCGRenderingIntentDefault);

    return [UIImage imageWithCGImage:newImg];

}

please share any idea about the above color changing….
what mistake i did in the code?..

Answer 1

I am not an IPhone programmer so I can’t test anything but some things are odd in your code:

Pixel size
When reading your data, you seem to assume you have a 32bits ARGB picture, did you validate it’s the case?

CFDataGetBytePtr
According to the docs, it Returns a read-only pointer to the bytes of a CFData object., are you sure you’re not looking for CFDataGetBytes which Copies the byte contents of a CFData object to an external buffer. In which case you’ll have to allocate your buffer to contain width * height * bpp. Once you have this copy, you can manipulate it anyway you want to create the new picture.

Pixel Selection
According to your question, I seem to understand that you want to change skin color from White to Black. Your current code iterates over every pixel to change its color. You should evaluate the “distance” between the pixel color and what you’re looking for, and if it’s below a certain threshold process it. It might be easier to perform the operation in HSV than by dealing with RGB colors.