how to draw UIImage image such as fit out style - ios

Question

I want to get the thumbnail from the jpg file and display as a UIImage. The display style is fit out mode, such as the UIViewContentModeScaleAspectFill. below is the sample code, but it is too complicate.
-(UIImage*)scaleToSize:(CGSize)size
{
CGFloat width = CGImageGetWidth(self.CGImage);
CGFloat height = CGImageGetHeight(self.CGImage);
NSLog(#"size w=%f, h=%f, image w=%f, h=%f", size.width, size.height, width, height);
float verticalRadio = size.height*1.0/height;
float horizontalRadio = size.width*1.0/width;
float radio = 1;
if(verticalRadio>1 && horizontalRadio>1)
{
radio = verticalRadio > horizontalRadio ? horizontalRadio : verticalRadio;
}
else
{
radio = verticalRadio < horizontalRadio ? verticalRadio : horizontalRadio;
}
width = width*radio;
height = height*radio;
NSLog(#"width=%f, height=%f", width, height);
int xPos = (size.width - width)/2;
int yPos = (size.height-height)/2;
NSLog(#"xpos=%d, ypos=%d", xPos, yPos);
CGSize sz = CGSizeMake(width, height);
UIGraphicsBeginImageContext(sz);
//
[self drawInRect:CGRectMake(0, 0, width, height)];
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGRect rt = CGRectMake(-xPos, -yPos, size.width, size.height);
UIImage* thub = [scaledImage getSubImage:rt];
scaledImage = nil;
return thub;
}
- (UIImage *)getSubImage:(CGRect) rect{
CGImageRef subImageRef = CGImageCreateWithImageInRect(self.CGImage, rect);
CGRect smallBounds = CGRectMake(rect.origin.x, rect.origin.y, CGImageGetWidth(subImageRef), CGImageGetHeight(subImageRef));
NSLog(#"small bounds x=%f, y=%f, w=%f, h=%f", smallBounds.origin.x, smallBounds.origin.y, smallBounds.size.width, smallBounds.size.height);
UIGraphicsBeginImageContext(smallBounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, smallBounds, subImageRef);
UIImage* smallImg = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();
return smallImg;
}

Answer 1

I have update the method:
-(UIImage*)getSubImage:(CGSize)size
{
CGFloat width = CGImageGetWidth(self.CGImage);
CGFloat height = CGImageGetHeight(self.CGImage);
float verticalRadio = size.height*1.0/height;
float horizontalRadio = size.width*1.0/width;
float radio = 1;
radio = verticalRadio < horizontalRadio ? horizontalRadio : verticalRadio;
CGRect displayRect = CGRectMake((size.width - width*radio)/2.0f,
(size.height-height*radio)/2.0f,
width*radio,
height*radio);
// create a bitmap context and then set the context to current using
UIGraphicsBeginImageContext(size);
//clip
UIRectClip(displayRect);
//draw the bitmap in rect
[self drawInRect:displayRect];
// from context to get a UIIMage
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
// move context out of buffer
UIGraphicsEndImageContext();
NSLog(#"getSubImage ---->");
// return.
return scaledImage;
}