polaroid filter from UIImage

Question

I am trying to implement some image filters, like polaroid, in iphone. I searched on how to filter an existing UIImage to convert it into a polaroid style and come across th

Answer 1

     int step=10;// variable value that changes the level of saturation

int red = pixelRedVal;
int green = pixelGreenVal;
int blue = pixelBlueVal;

int avg = (red + green + blue) / 3;

pixelBuf[r] = SAFECOLOR((avg + step * (red - avg)));
pixelBuf[g] = SAFECOLOR((avg + step * (green - avg)));
pixelBuf[b] = SAFECOLOR((avg + step * (blue - avg)));
where SAFECOLOR is a macro

define SAFECOLOR(color) MIN(255,MAX(0,color))
and for Brightness int step=10;// variable value that changes the level of saturation

int red = pixelRedVal;
int green = pixelGreenVal;
int blue = pixelBlueVal;


pixelBuf[r] = SAFECOLOR(red * step);
pixelBuf[g] = SAFECOLOR(green * step);
pixelBuf[b] = SAFECOLOR(blue * step);




You can simply use this: with different parameters

// Note: the hue input ranges from 0.0 to 1.0, both red.  Values outside this range will be clamped to 0.0 or 1.0.
    //Polaroid with HSB parameter

   - (UIImage*) polaroidishEffectWithHue:(CGFloat)hue saturation:(CGFloat)sat brightness:(CGFloat)bright  alpha:(CGFloat)alpha
  {

   // Find the image dimensions.
    CGSize imageSize = [self size];
    CGRect imageExtent = CGRectMake(0,0,imageSize.width,imageSize.height);

    // Create a context containing the image.
    UIGraphicsBeginImageContext(imageSize);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self drawAtPoint:CGPointMake(0,0)];

    // Draw the hue on top of the image.
    CGContextSetBlendMode(context, kCGBlendModeHue);
    [[UIColor colorWithHue:hue saturation:sat brightness:bright alpha:alpha] set];
    UIBezierPath *imagePath = [UIBezierPath bezierPathWithRect:imageExtent];
    [imagePath fill];

    // Retrieve the new image.
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return result;
}

Answer 2

This might be helpful, from Camera+ taking filters from photoshop and reproducing them for iOS.

http://taptaptap.com/blog/creating-a-camera-plus-fx/