kCAFilter最近放大过滤器（UIImageView）

Question

我正在使用在这里找到的 QREncoder 库： https://github.com/jverkoey/ObjQREncoder

基本上，我查看了该作者的示例代码，当他创建 QRCode 时，它​​完美地显示出来，没有像素化。该库提供的图像本身是 33 x 33 像素，但他使用 kCAFilterNearest 来放大并使其非常清晰（无像素化）。这是他的代码：

    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];

我在 xib 中有一个 UIImageView，我将其图像设置为这样：

[[template imageVQRCode] setImage:[QREncoder encode:ticketNum]];
[[[template imageVQRCode] layer] setMagnificationFilter:kCAFilterNearest];

但是 qrcode 真的很模糊。在示例中，结果非常清晰。 我做错了什么？ 谢谢！

更新：我发现问题不在于缩放，也不与 kCAFFilterNearest 有关。它与从视图生成 PNG 图像有关。 这是它在设备上的外观与我将 UIView 保存到 PNG 表示形式时的外观（注意 QRCodes 质量）：

更新 2：这就是我从 UIView 生成 PNG 文件的方式：

   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

我使用以下功能来编辑图像。

- (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);

请找到下面的图片，如果您需要任何帮助，请告诉我。