Question

I am new to developing code in iPhone, and I want to search some code to resize my UIImage to a specified size but keep the ratio. The specified size is something like a frame that the image can’t come cross the boundary, within that boundary the image should scale to fit the frame and keep the ratio, the code I am currently using can do resize but can’t keep the ratio, just paste it here to see if I can do some trivial modifications so that it can make it possible.

- (UIImage *)resizeImage:(UIImage*)image newSize:(CGSize)newSize {
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGImageRef imageRef = image.CGImage;

UIGraphicsBeginImageContextWithOptions(newSize, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();

// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height);

CGContextConcatCTM(context, flipVertical);  
// Draw into the context; this scales the image
CGContextDrawImage(context, newRect, imageRef);

// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(context);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

CGImageRelease(newImageRef);
UIGraphicsEndImageContext();    

return newImage;

}

Answer 1

well, you could resize the image a bit simpler:

+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}

Then you need to calculate a new size that maintenance the aspect ratio.
e.g. to get a image Half the size you would provide a size created like this:

  CGSize halfSize = CGSizeMake(image.size.width*0.5, image.size.height*0.5);