GPUImage色度键过滤器 [英] GPUImage Chroma Key filter

问题描述

我想使用GPUImage框架的chromakey过滤器。我按照Filtershowcase示例，但显然我错过了一些东西，因为它只显示视频，但没有绿屏幕键效果。这是我的视频摄像头/过滤器的初始化：

I am trying to use the GPUImage framework's chromakey filter. I followed the Filtershowcase example, but obviously I am missed something becuase it only shows the video, but no green screen keying out effect. Here's my initialization of video camera/filter:

camera = [[GPUImageStillCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480
                                             cameraPosition:AVCaptureDevicePositionBack];
camera.outputImageOrientation = UIInterfaceOrientationLandscapeLeft;
camera.horizontallyMirrorFrontFacingCamera = NO;
camera.horizontallyMirrorRearFacingCamera = NO;


chromaKeyFilter = [[GPUImageChromaKeyFilter alloc] init];
chromaKeyFilter.thresholdSensitivity = sliderThres.value;

UIImage *inputImage = [UIImage imageNamed:@"WID-small.jpg"];


GPUImagePicture *sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage
                                                    smoothlyScaleOutput:YES];


[camera addTarget:chromaKeyFilter];
[sourcePicture addTarget:chromaKeyFilter];
[sourcePicture processImage];

[chromaKeyFilter addTarget:viewCamera];


[camera startCameraCapture];

所以camera和sourcePicture都进入过滤器，比viewCamera过滤。但现在，我只看到平原的视频，没有chromakey效果。 （我有一个滑块来改变阈值）。

So camera and sourcePicture both feed into the filter, filter than goes into viewCamera. But right now, I only see the plain video, no chromakey effect. (I have a slider that alters the threshold).

UPDATED 与GPUImageChromaKeyBlendFilter

UPDATED with GPUImageChromaKeyBlendFilter

camera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionBack];
camera.outputImageOrientation = UIInterfaceOrientationLandscapeLeft;
chromaKeyFilter = [[GPUImageChromaKeyBlendFilter alloc] init];


UIImage *inputImage;
inputImage = [UIImage imageNamed:@"WID-small.jpg"];
GPUImagePicture *sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];


[camera addTarget:chromaKeyFilter];
[sourcePicture processImage];
[sourcePicture addTarget:chromaKeyFilter];
[chromaKeyFilter addTarget:viewCamera];

[camera startCameraCapture];

使用此过滤器，只需将其替换为黑色，而不是实际图像。

With this filter, it simply replaced it with black, not the actual image.

推荐答案

经过几天的尝试后发现这个宝石.... 。显然，你假设要挂在（强ref）到GPUImagePicture。我的印象是，内部的过滤器链将有一个强的引用，但事实并非如此。保持它作为实例var解决了这个问题。

Found this gem after a couple of days of trying..... Apparently you are suppose to hang on (strong ref) to GPUImagePicture. I was under the impression that the filter chain internally would have a strong reference, but that's not the case. Keeping it as instance var solved the problem.

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