renderInContext image drawing with specified size - ios

Question

How to draw smaller image than size of context without using CGAffineTransform?
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
// center image
CGContextTranslateCTM(context, placement.origin.x, placement.origin.y);
[imageView.layer renderInContext:context];
The problem is that if imageView.image.size is bigger than size it will be drawn centered, but cut at borders (bigger image than drawing area). I want the image to fit, so would like to decrease size of imageView.image.size. Is there any way to achieve this using renderInContext?

Answer 1

Via [imageView.layer renderInContext:context]; you can't change the size (or i didn't find a way). The only option to do so, is to create now image with drawImage (on requested size), allocate new UIImageView and draw its layer.
UIImage *resizedImage = [self createNewImageFrom:currentImage withSize:size];
UIImageView *imageView = [[UIImageView alloc] initWithImage:resizedImage];
// ...
[imageView.layer renderInContext:context];
- (UIImage*)createNewImageFrom:(UIImage*)image withSize:(CGSize)size {
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0f, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), image.CGImage);
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}

Answer 2

Why do you want to do this without transforming the context? It's the exact right tool for the job!
The simplest way here would be to call CGContextScaleCTM to apply a scale factor to the context. That scale factor will effect all drawing to the context, including the call to -renderIntoContext:.

Answer 3

this is version for scaled size, just replace scale with size.width and size.height for any target size.
for UIView:
-(UIImage*)convertViewToImage:(UIView*)v withScale:(float)scale{
//create bitmap context with scaled size
CGSize s = v.bounds.size;
s.width *= scale;
s.height *= scale;
UIGraphicsBeginImageContextWithOptions(s, NO, [UIScreen mainScreen].scale);
//scale CTM to render and resotre CTM
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextScaleCTM(context, scale, scale);
[v.layer renderInContext: context];
CGContextRestoreGState(context);
UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
for UIScrollView
-(UIImage*)convertScrollContentToImage:(UIScrollView*)sv withScale:(float)scale{
//create bitmap context with scaled size
CGSize s = sv.contentSize;
s.width *= scale;
s.height *= scale;
UIGraphicsBeginImageContextWithOptions(s, NO, [UIScreen mainScreen].scale);
{
//set scroll.frame.size to contentSize, and contentOffset to 0
CGPoint savedContentOffset = sv.contentOffset;
CGRect savedFrame = sv.frame;
sv.contentOffset = CGPointZero;
sv.frame = CGRectMake(0, 0, sv.contentSize.width, sv.contentSize.height);
//scale CTM to render and resotre CTM
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextScaleCTM(context, scale, scale);
[sv.layer renderInContext: context];
CGContextRestoreGState(context);
//set scroll.frame.size and ContentOffset back
sv.contentOffset = savedContentOffset;
sv.frame = savedFrame;
}
UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}