GPUImage：GPUImageThreeInputFilter適用於靜態圖像輸入，但不適用於相機輸入

Question

我試圖使用GPUImage實現重新映射過濾器。它類似於opencv重映射函數，它使用輸入圖像xmap和ymap。所以，我繼承了GPUImageThreeInputFilter並編寫了我自己的着色器代碼。當過濾器的輸入仍然是圖像時，我得到正確的輸出圖像。代碼如下：

GPUImageRemap *remapFilter=[[GPUImageRemap alloc] init]; 
    [remapFilter forceProcessingAtSize:CGSizeMake(sphericalImageW, sphericalImageH)]; 
    UIImage *inputImage = [UIImage imageNamed:@"test.jpg"]; 
    GPUImagePicture *stillImageSource = [[GPUImagePicture alloc] initWithImage:inputImage]; 
    [stillImageSource addTarget:remapFilter atTextureLocation:0]; 
    GPUImagePicture *stillImageSource1 = [[GPUImagePicture alloc] initWithImage:xmapImage]; 
    [stillImageSource1 processImage]; 
    [stillImageSource1 addTarget:remapFilter atTextureLocation:1]; 
    GPUImagePicture *stillImageSource2 = [[GPUImagePicture alloc] initWithImage:ymapImage]; 
    [stillImageSource2 processImage]; 
    [stillImageSource2 addTarget:remapFilter atTextureLocation:2]; 
    [stillImageSource processImage]; 
    UIImage *filteredImage=[remapFilter imageFromCurrentlyProcessedOutput]; 

但是，當輸入切換到相機輸入時，我得到了錯誤的輸出圖像。我做了一些調試，發現xmap和ymap沒有加載到第二個和第三個紋理。這2個紋理的像素值均爲0

videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPresetHigh cameraPosition:AVCaptureDevicePositionFront]; 
    videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait; 
    GPUImageRemap *remapFilter=[[GPUImageRemap alloc] init]; 
    [remapFilter forceProcessingAtSize:CGSizeMake(sphericalImageW, sphericalImageH)]; 
    [videoCamera addTarget:remapFilter atTextureLocation:0]; 
    GPUImagePicture *stillImageSource1 = [[GPUImagePicture alloc] initWithImage:xmapImage]; 
    [stillImageSource1 processImage]; 
    [stillImageSource1 addTarget:remapFilter atTextureLocation:1]; 
    GPUImagePicture *stillImageSource2 = [[GPUImagePicture alloc] initWithImage:ymapImage]; 
    [stillImageSource2 processImage]; 
    [stillImageSource2 addTarget:remapFilter atTextureLocation:2]; 

    GPUImageView *camView = [[GPUImageView alloc] initWithFrame:self.view.bounds]; 
    [remapFilter addTarget:camView]; 
    [videoCamera startCameraCapture]; 

頭文件：

#import <GPUImage.h> 
#import <GPUImageThreeInputFilter.h> 

@interface GPUImageRemap : GPUImageThreeInputFilter 
{ 
} 

主要文件：

#import "GPUImageRemap.h" 


NSString *const kGPUImageRemapFragmentShaderString = SHADER_STRING 
(

varying highp vec2 textureCoordinate; 
varying highp vec2 textureCoordinate2; 
    varying highp vec2 textureCoordinate3; 

uniform sampler2D inputImageTexture; 
uniform sampler2D inputImageTexture2; 
    uniform sampler2D inputImageTexture3; 

/* 
x, y map orignally store floating point numbers in [0 imageWidth] and [0 imageHeight] 
then they are divided by imageWidth-1 and imageHeight-1 to be in [0 1] 
then they are converted to integer by multiply 1000000 
then an integer is put in the 4 byte of RGBA channel 
then each unsigned byte RGBA component is clamped to [0 1] and passed to fragment shader 
therefore, do the inverse in fragment shader to get original x, y coordinates 
*/ 
void main() 
{ 
    highp vec4 xAry0_1 = texture2D(inputImageTexture2, textureCoordinate2); 
    highp vec4 xAry0_255=floor(xAry0_1*vec4(255.0)+vec4(0.5)); 
    //largest integer number we may see will not exceed 2000000, so 3 bytes are enough to carry our integer values 
    highp float xint=xAry0_255.b*exp2(16.0)+xAry0_255.g*exp2(8.0)+xAry0_255.r; 
    highp float x=xint/1000000.0; 

    highp vec4 yAry0_1 = texture2D(inputImageTexture3, textureCoordinate3); 
    highp vec4 yAry0_255=floor(yAry0_1*vec4(255.0)+vec4(0.5)); 
    highp float yint=yAry0_255.b*exp2(16.0)+yAry0_255.g*exp2(8.0)+yAry0_255.r; 
    highp float y=yint/1000000.0; 

    if (x<0.0 || x>1.0 || y<0.0 || y>1.0) 
    { 
     gl_FragColor = vec4(0,0,0,1); 
    } 
    else 
    { 
     highp vec2 imgTexCoord=vec2(y, x); 
     gl_FragColor = texture2D(inputImageTexture, imgTexCoord); 
    } 
} 
); 

@implementation GPUImageRemap 

- (id)init 
{ 
    if (!(self = [super initWithFragmentShaderFromString:kGPUImageRemapFragmentShaderString])) 
    { 
     return nil; 
    } 
    return self; 
} 

Answer 1

我找到了答案我自己。 GPUImagePicture不能被聲明爲局部變量。否則，它在函數退出後被釋放。這就是爲什麼當他們上傳到GPU時他們都是0。所有的GPUImagePicture變量都需要是全局的。