Image resizing and masking in IOS

Resize UIImage :

+(UIImage *)resizeImage:(UIImage *)image toSize:(CGSize)destSize{

    float currentHeight = image.size.height;

    float currentWidth = image.size.width;

    float liChange ;

    CGSize newSize ;

    if(currentWidth == currentHeight) // image is square

        {

             liChange = destSize.height / currentHeight;

             newSize.height = currentHeight * liChange;

             newSize.width = currentWidth * liChange;

            }

    else if(currentHeight > currentWidth) // image is landscape

         {

              liChange = destSize.width / currentWidth;

              newSize.height = currentHeight * liChange;

              newSize.width = destSize.width;

             }

    else        // image is Portrait

         {

             liChange = destSize.height / currentHeight;

             newSize.height= destSize.height;

             newSize.width = currentWidth * liChange;

             }

    

    

    UIGraphicsBeginImageContext( newSize );

    CGContextRef    context;

    UIImage      *outputImage = nil;

    

    context = UIGraphicsGetCurrentContext();

    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);

    [image drawInRect:CGRectMake( 0, 0, newSize.width, newSize.height )];

    outputImage = UIGraphicsGetImageFromCurrentImageContext();

    

    UIGraphicsEndImageContext();

    

    CGImageRef imageRef;

    int x = (newSize.width == destSize.width) ? 0 : (newSize.width - destSize.width)/2;

    int y = (newSize.height == destSize.height) ? 0 : (newSize.height - destSize.height )/2;

    if ( ( imageRef = CGImageCreateWithImageInRect( outputImage.CGImage, CGRectMake(x, y, destSize.width, destSize.height) ) ) ) {

         outputImage = [[UIImage alloc] initWithCGImage: imageRef] ;

         CGImageRelease( imageRef );

        }

     

    return outputImage;

}

Mask image:

+(UIImage *)maskImage:(UIImage *)image andMaskingImage:(UIImage *)maskingImage{

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGImageRef maskImageRef = [maskingImage CGImage];

    CGContextRef mainViewContentContext = CGBitmapContextCreate (NULL, maskingImage.size.width, maskingImage.size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);

    if (mainViewContentContext==NULL)

         return NULL;

    CGFloat ratio = 0;

    ratio = maskingImage.size.width/ image.size.width;

    if(ratio * image.size.height < maskingImage.size.height) {

         ratio = maskingImage.size.height/ image.size.height;

        }

    CGRect rect1= {{0, 0}, {maskingImage.size.width, maskingImage.size.height}};

    CGRect rect2= {{-((image.size.width*ratio)-maskingImage.size.width)/2 , -((image.size.height*ratio)-maskingImage.size.height)/2}, {image.size.width*ratio, image.size.height*ratio}};

    CGContextClipToMask(mainViewContentContext, rect1, maskImageRef);

    CGContextDrawImage(mainViewContentContext, rect2, image.CGImage);

    CGImageRef newImage = CGBitmapContextCreateImage(mainViewContentContext);

    CGContextRelease(mainViewContentContext);

    UIImage *theImage = [UIImage imageWithCGImage:newImage];

    CGImageRelease(newImage);

     // return the image

    return theImage;

}

More details please visit following link

http://mobiledevelopertips.com/cocoa/how-to-mask-an-image.html