xcode CIFilter guassianBlur 和 boxBlur 正在缩小图像 - 如何避免调整大小？
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CIFilter guassianBlur and boxBlur are shrinking the image - how to avoid the resizing?
提问by foundry
I am taking a snapshot of the contents of an NSView, applying a CIFilter, and placing the result back into the view. If the CIFilteris a form of blur, such as CIBoxBluror CIGuassianBlur, the filtered result is slightly smaller than the original. As I am doing this iteratively the result becomes increasingly small, which I want to avoid.
我正在对 an 的内容进行快照NSView，应用 aCIFilter并将结果放回视图中。如果CIFilter是一种模糊形式，例如CIBoxBlur或CIGuassianBlur，则过滤后的结果会比原始结果略小。当我迭代地这样做时，结果变得越来越小，我想避免这种情况。
The issue is alluded to herealbeit in a slightly different context (Quartz Composer). Apple FunHousedemo app applies a Guassian blurwithout the image shrinking, but I haven't yet worked out how this app does it (it seems to be using OpenGLwhich I am not familiar with).
此问题已提到了这里的一个稍微不同的上下文（石英作曲家）虽然。AppleFunHouse演示应用程序应用了一个Guassian blur没有图像缩小的应用程序，但我还没有弄清楚这个应用程序是如何做到的（它似乎正在使用OpenGL我不熟悉的）。
Here is the relevant part of the code (inside an NSViewsubclass)
这是代码的相关部分（在NSView子类中）
NSImage* background = [[NSImage alloc] initWithData:[self dataWithPDFInsideRect:[self bounds]]];
CIContext* context = [[NSGraphicsContext currentContext] CIContext];
CIImage* ciImage = [background ciImage];
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"
keysAndValues: kCIInputImageKey, ciImage,
@"inputRadius", [NSNumber numberWithFloat:10.0], nil];
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGImageRef cgImage = [context createCGImage:result
fromRect:[result extent]];
NSImage* newBackground = [[NSImage alloc] initWithCGImage:cgImage size:background.size];
If I try a color-changing filter such as CISepiaTone, which is not shifting pixels around, the shrinking does not occur.
如果我尝试使用CISepiaTone不会移动像素的变色滤镜，例如，则不会发生缩小。
I am wondering if there is a quick fix that doesn't involve diving into openGL?
我想知道是否有不涉及潜入的快速修复openGL？
回答by BBC_Z
They're actually not shrinking the image, they're expanding it (I think by 7 pixels around all edges) and the default UIView 'scale To View' makes it looks like it's been shrunk.
他们实际上并没有缩小图像，而是扩大了它（我认为所有边缘周围都扩大了 7 个像素），并且默认的 UIView 'scale To View' 使它看起来像被缩小了。
Crop your CIImage with:
使用以下方法裁剪您的 CIImage：
CIImage *cropped=[output imageByCroppingToRect:CGRectMake(0, 0, view.bounds.size.width*scale, view.bounds.size.height*scale)];
where view is the original bounds of your NSView that you drew into and 'scale' is your [UIScreen mainScreen] scale].
其中 view 是您绘制的 NSView 的原始边界，'scale' 是您的 [UIScreen mainScreen] 比例]。
回答by ccgus
You probably want to clamp your image before using the blur:
您可能想在使用模糊之前夹住图像：
- (CIImage*)imageByClampingToExtent {
CIFilter *clamp = [CIFilter filterWithName:@"CIAffineClamp"];
[clamp setValue:[NSAffineTransform transform] forKey:@"inputTransform"];
[clamp setValue:self forKey:@"inputImage"];
return [clamp valueForKey:@"outputImage"];
}
Then blur, and then crop to the original extent. You'll get non-transparent edges this way.
然后模糊，然后裁剪到原始范围。这样你会得到不透明的边缘。
回答by IluTov
@BBC_Z's solution is correct.
@BBC_Z 的解决方案是正确的。
Although I find it more elegant to crop not according to the view, but to the image.
And you can cut away the useless blurred edges:
虽然我发现不是根据视图而是根据图像裁剪更优雅。
你可以剪掉无用的模糊边缘：
// Crop transparent edges from blur
resultImage = [resultImage imageByCroppingToRect:(CGRect){
.origin.x = blurRadius,
.origin.y = blurRadius,
.size.width = originalCIImage.extent.size.width - blurRadius*2,
.size.height = originalCIImage.extent.size.height - blurRadius*2
}];
