kCAFilterNearest maginifcation filter (UIImageView) - objective-c

Question

I am using QREncoder library found here: https://github.com/jverkoey/ObjQREncoder
Basically, i looked at the example code by this author, and when he creates the QRCode it comes out perfectly with no pixelation. The image itself that the library provides is 33 x 33 pixels, but he uses kCAFilterNearest to magnify and make it very clear (no pixilation). Here is his code:
UIImage* image = [QREncoder encode:#"http://www.google.com/"];
UIImageView* imageView = [[UIImageView alloc] initWithImage:image];
CGFloat qrSize = self.view.bounds.size.width - kPadding * 2;
imageView.frame = CGRectMake(kPadding, (self.view.bounds.size.height - qrSize) / 2,
qrSize, qrSize);
[imageView layer].magnificationFilter = kCAFilterNearest;
[self.view addSubview:imageView];
I have a UIImageView in a xib, and I am setting it's image like this:
[[template imageVQRCode] setImage:[QREncoder encode:ticketNum]];
[[[template imageVQRCode] layer] setMagnificationFilter:kCAFilterNearest];
but the qrcode is really blurry. In the example, it comes out crystal clear.
What am i doing wrong?
Thanks!
UPDATE:I found out that the problem isn't with scaling or anything to do with kCAFFilterNearest. It has to do with generating the PNG image from the view. Here's how it looks on the deive vs how it looks like when i save the UIView to the PNG representation (Notice the QRCodes quality):
UPDATE 2: This is how I am generating the PNG file from UIView:
UIGraphicsBeginImageContextWithOptions([[template view] bounds].size, YES, 0.0);
[[[template view] layer] renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[UIImagePNGRepresentation(viewImage) writeToFile:plistPath atomically:YES];

Answer 1

I have used below function for editing image.
- (UIImage *)resizedImage:(CGSize)newSize interpolationQuality:(CGInterpolationQuality)quality
{
BOOL drawTransposed;
switch (self.imageOrientation) {
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
drawTransposed = YES;
break;
default:
drawTransposed = NO;
}
return [self resizedImage:newSize
transform:[self transformForOrientation:newSize]
drawTransposed:drawTransposed
interpolationQuality:quality];
}
- (UIImage *)resizedImage:(CGSize)newSize
transform:(CGAffineTransform)transform
drawTransposed:(BOOL)transpose
interpolationQuality:(CGInterpolationQuality)quality
{
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
CGImageRef imageRef = self.CGImage;
// Build a context that's the same dimensions as the new size
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
if((bitmapInfo == kCGImageAlphaLast) || (bitmapInfo == kCGImageAlphaNone))
bitmapInfo = kCGImageAlphaNoneSkipLast;
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
bitmapInfo);
// Rotate and/or flip the image if required by its orientation
CGContextConcatCTM(bitmap, transform);
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(bitmap, quality);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
return newImage;
}
UIImageWriteToSavedPhotosAlbum([image resizedImage:CGSizeMake(300, 300) interpolationQuality:kCGInterpolationNone], nil, nil, nil);
Please find below image and let me know if you need any help.