Resizing a photo to a new UIImage

[evan1466]

-(UIImage*)imageByScalingProportionallyToMinimumSize:(UIImage *)imageIn :(CGSize)targetSize{	
	UIImage *sourceImage = imageIn;
	CGSize imageSize = sourceImage.size;
	CGFloat width = imageSize.width;
	CGFloat height = imageSize.height;
	CGFloat targetWidth = targetSize.width;
	CGFloat targetHeight = targetSize.height;    
    if([[UIScreen mainScreen]respondsToSelector:@selector(scale)]&&(UI_USER_INTERFACE_IDIOM() != UIUserInterfaceIdiomPad)) { 
		CGFloat scale = [[UIScreen mainScreen] scale];
		targetWidth = targetWidth*scale;
		targetHeight = targetHeight*scale;
	}
	CGFloat scaleFactor = 1.0;
	CGFloat scaledWidth = targetWidth;
	CGFloat scaledHeight = targetHeight;
	
	CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
	
	if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
		
		CGFloat widthFactor = targetWidth / width;
		CGFloat heightFactor = targetHeight / height;
		
		if (widthFactor > heightFactor)
			scaleFactor = widthFactor;
		else
			scaleFactor = heightFactor;
		
		scaledWidth  = width * scaleFactor;
		scaledHeight = height * scaleFactor;
		
		if (widthFactor > heightFactor) {
			thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
		} else if (widthFactor < heightFactor) {
			thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
		}
	}
	CGImageRef imageRef = [sourceImage CGImage];
	CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);
	CGColorSpaceRef colorSpaceInfo = CGColorSpaceCreateDeviceRGB();
	
	if (alphaInfo == kCGImageAlphaNone)
		alphaInfo = kCGImageAlphaNoneSkipLast;
	
	CGContextRef bitmap;
	
	if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
		bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), 4*targetWidth, colorSpaceInfo, alphaInfo);
		
	} else {
		bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), 4*targetWidth, colorSpaceInfo, alphaInfo);
		
	}
	if (sourceImage.imageOrientation == UIImageOrientationLeft) {
		NSLog(@"image orientation left");
		CGContextRotateCTM (bitmap, radians(90));
		CGContextTranslateCTM (bitmap, 0, -height);
		
	} else if (sourceImage.imageOrientation == UIImageOrientationRight) {
		NSLog(@"image orientation right");
		CGContextRotateCTM (bitmap, radians(-90));
		CGContextTranslateCTM (bitmap, -width, 0);
		
	} else if (sourceImage.imageOrientation == UIImageOrientationUp) {
		NSLog(@"image orientation up");	
		
	} else if (sourceImage.imageOrientation == UIImageOrientationDown) {
		NSLog(@"image orientation down");	
		CGContextTranslateCTM (bitmap, targetWidth,targetHeight);
		CGContextRotateCTM (bitmap, radians(-180.));
	}
    
	CGContextDrawImage(bitmap, CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledWidth, scaledHeight), imageRef);
	CGImageRef ref = CGBitmapContextCreateImage(bitmap);
	UIImage *result;
    if([[UIScreen mainScreen]respondsToSelector:@selector(scale)]&&(UI_USER_INTERFACE_IDIOM() != UIUserInterfaceIdiomPad)) { 
		float scale = [[UIScreen mainScreen] scale];
		result = [UIImage imageWithCGImage:ref scale:scale orientation:UIImageOrientationUp];
	} else {
		result = [UIImage imageWithCGImage:ref];
	}
	CGColorSpaceRelease(colorSpaceInfo);
	CGContextRelease(bitmap);
	CGImageRelease(ref);
	
	return result;	
}

[cmezak]

Originally Posted by evan1466

So I am using very similar code to what is above.

Have been having issues resizing PNGs but only in the simulator.

Any thoughts?

CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component colorspace; kCGImageAlphaLast; 970 bytes/row.

It's been a long time since I've participated in this thread. I'm now using code from this fella to handle my image resizing:

Resize a UIImage the right way — Trevor’s Bike Shed

Good luck!

[evan1466]

So looking into it his code has the same issue on the simulator.

Something with the alpha setting on the PNGs isn't flowing through and causes the unsupported warning.

Oddly it works on the device, which I guess is all that really matters...

Originally Posted by cmezak

It's been a long time since I've participated in this thread. I'm now using code from this fella to handle my image resizing:

Resize a UIImage the right way — Trevor’s Bike Shed

Good luck!