Question

感谢您的光临。

这是我的代码

 CIImage *result = _vignette.outputImage;
self.mainImageView.image = nil;
//self.mainImageView.contentMode = UIViewContentModeScaleAspectFit;
self.mainImageView.image = [UIImage imageWithCIImage:result];
self.mainImageView.contentMode = UIViewContentModeScaleAspectFit;

在这里_vignette正确设置过滤器，图像效果正确应用于图像。

我正在使用分辨率为500x375的源图像。我的imageView几乎拥有iPhone屏幕的分辨率。所以为了避免拉伸，我正在使用AspectFit。

但是在我将结果图像分配回我的imageView后应用效果后，它会拉伸。无论我使用哪个UIViewContentMode。它不起作用。无论我给出的过滤器如何，它似乎总是适用ScaleToFill。

知道为什么会这样吗？任何建议都受到高度赞赏。

Answer 1

（1）Aspect Fit 拉伸图像 - 以适应。如果您根本不想拉伸图像，请使用中心（例如）。

（2）imageWithCIImage给你一个非常奇怪的野兽，一个不基于CGImage的UIImage，因此不受普通的图层显示规则的影响。它实际上只不过是CIImage的薄包装，这不是你想要的。你必须通过CGImage将CIFilter输出转换（渲染）到UIImage，从而为你提供一个实际上有一些位的UIImage（CGImage，一个位图）。我在这里的讨论为您提供了演示代码：

http://www.apeth.com/iOSBook/ch15.html#_cifilter_and_ciimage

换句话说，在某些时候，您必须调用CIContext createCGImage:fromRect:从CIFilter的输出生成CGImageRef，并将其传递给UIImage。在您这样做之前，您没有将过滤器操作的输出作为真正的UIImage。

或者，您可以将图像从imageWithCIImage绘制到图形上下文中。例如，您可以将其绘制到图像图形上下文中，然后使用那个图像。

无法做的是直接显示imageWithCIImage的图像。那是因为它不是图像！它没有底层位图（CGImage）。那里没有。它只是一组用于导出图像的CIFilter指令。

Answer 2

我只是花了一整天时间。我遇到定向问题，然后输出质量差。

使用相机拍摄图像后，我会这样做。

NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                UIImage *image = [[UIImage alloc] initWithData:imageData];

这会导致旋转问题，所以我需要这样做。

UIImage *scaleAndRotateImage(UIImage *image)
{
    int kMaxResolution = image.size.height; // Or whatever

    CGImageRef imgRef = image.CGImage;

    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);

    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);
    if (width > kMaxResolution || height > kMaxResolution) {
        CGFloat ratio = width/height;
        if (ratio > 1) {
            bounds.size.width = kMaxResolution;
            bounds.size.height = bounds.size.width / ratio;
        }
        else {
            bounds.size.height = kMaxResolution;
            bounds.size.width = bounds.size.height * ratio;
        }
    }

    CGFloat scaleRatio = bounds.size.width / width;
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
    CGFloat boundHeight;
    UIImageOrientation orient = image.imageOrientation;
    switch(orient) {

        case UIImageOrientationUp: //EXIF = 1
            transform = CGAffineTransformIdentity;
            break;

        case UIImageOrientationUpMirrored: //EXIF = 2
            transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;

        case UIImageOrientationDown: //EXIF = 3
            transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationDownMirrored: //EXIF = 4
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;

        case UIImageOrientationLeftMirrored: //EXIF = 5
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationLeft: //EXIF = 6
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationRightMirrored: //EXIF = 7
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        case UIImageOrientationRight: //EXIF = 8
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        default:
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

    }

    UIGraphicsBeginImageContext(bounds.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
    }
    else {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
    }

    CGContextConcatCTM(context, transform);

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();  

    return imageCopy;  
}

然后当我应用我的过滤器时，我这样做（特别感谢这个线程 - 特别是亚光和Wex）

    -(UIImage*)processImage:(UIImage*)image {

            CIImage *inImage = [CIImage imageWithCGImage:image.CGImage];

            CIFilter *filter = [CIFilter filterWithName:@"CIColorControls" keysAndValues:
                        kCIInputImageKey, inImage,
                        @"inputContrast", [NSNumber numberWithFloat:1.0],
                        nil];

    UIImage *outImage = [filter outputImage];

//Juicy bit
            CGImageRef cgimageref = [[CIContext contextWithOptions:nil] createCGImage:outImage fromRect:[outImage extent]];

            return [UIImage imageWithCGImage:cgimageref];
        }

应用CIFIlter后设置UIImageView内容模式

2 个答案: