I am trying to create a partial Grayscale image - ios

Question

I am trying to create a partial gray scale image in which i am reading each and every pixel in that image and replacing the pixel data to gray color, and if the pixel color matches the desired color i restrict it to be applied so that the specific pixel color doesn't change.i don't know where i am going wrong it changes the whole image to gray scale and rotates the image 90 degrees. can some one help me out with this issue thanks in advance.
-(UIImage *) toPartialGrayscale{
const int RED = 1;
const int GREEN = 2;
const int BLUE = 3;
initialR=255.0;
initialG=0.0;
initialB=0.0;//218-112-214//0-191-255
float r;
float g;
float b;
tollerance=50;
// Create image rectangle with current image width/height
CGRect imageRect = CGRectMake(0, 0, originalImageView.image.size.width * scale, originalImageView.image.size.height * scale);
int width = imageRect.size.width;
int height = imageRect.size.height;
// the pixels will be painted to this array
uint32_t *pixels = (uint32_t *) malloc(width * height * sizeof(uint32_t));
// clear the pixels so any transparency is preserved
memset(pixels, 0, width * height * sizeof(uint32_t));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// create a context with RGBA pixels
CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * sizeof(uint32_t), colorSpace,
kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
// paint the bitmap to our context which will fill in the pixels array
CGContextDrawImage(context, CGRectMake(0, 0, width, height), [originalImageView.image CGImage]);
for(int y = 0; y < height; y++)
{
for(int x = 0; x < width; x++)
{
uint8_t *rgbaPixel = (uint8_t *) &pixels[y * width + x];
// convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
uint8_t gray = (uint8_t) ((30 * rgbaPixel[RED] + 59 * rgbaPixel[GREEN] + 11 * rgbaPixel[BLUE]) / 100);
// set the pixels to grayi
r= initialR-rgbaPixel[RED];
g= initialG-rgbaPixel[GREEN];
b= initialB-rgbaPixel[BLUE];
if ((r<tollerance&&r>-tollerance)&&(g<tollerance&&g>-tollerance)&&(b<tollerance&&b>-tollerance))
{
rgbaPixel[RED] = (uint8_t)r;
rgbaPixel[GREEN] = (uint8_t)g;
rgbaPixel[BLUE] = (uint8_t)b;
}
else
{
rgbaPixel[RED] = gray;
rgbaPixel[GREEN] = gray;
rgbaPixel[BLUE] = gray;
}
}
}
// create a new CGImageRef from our context with the modified pixels
CGImageRef image = CGBitmapContextCreateImage(context);
// we're done with the context, color space, and pixels
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
free(pixels);
// make a new UIImage to return
UIImage *resultUIImage = [UIImage imageWithCGImage:image
scale:scale
orientation:UIImageOrientationUp];
// we're done with image now too
CGImageRelease(image);
return resultUIImage;
}
This is the code i am using any kind of help will be appreciated thanks again in advance.

Answer 1

Hopefully the orientation piece is easy enough to resolve by playing with the UIImageOrientationUp constant that you're passing in when you create the final image. Try left or right until you get what you need.
As for the threshold not working, can you verify that your "tollerance" really is behaving like you expect. Change it to 255 and see if the entire image retains it's color (it should). If it's still grey, then you know that your conditional statement is where the problem lies.