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我正在尝试将UIImage传递给 GLSL 着色器。片段着色器是：

varying highp vec2 textureCoordinate;

uniform sampler2D inputImageTexture;
uniform sampler2D inputImageTexture2;

void main()
{
  highp vec4 color = texture2D(inputImageTexture, textureCoordinate); 
  highp vec4 color2 = texture2D(inputImageTexture2, textureCoordinate);

  gl_FragColor = color * color2;

}

我想要做的是从相机发送图像并与纹理进行多重混合。当我只是从相机发送数据时，一切都很好。所以问题应该是向着色器发送另一个纹理。我这样做是这样的：

- (void)setTexture:(UIImage*)image forUniform:(NSString*)uniform {

  CGSize sizeOfImage = [image size];
  CGFloat scaleOfImage = [image scale];
  CGSize pixelSizeOfImage = CGSizeMake(scaleOfImage * sizeOfImage.width, scaleOfImage * sizeOfImage.height);

  //create context
  GLubyte * spriteData = (GLubyte *)malloc(pixelSizeOfImage.width * pixelSizeOfImage.height * 4 * sizeof(GLubyte));
  CGContextRef spriteContext = CGBitmapContextCreate(spriteData, pixelSizeOfImage.width, pixelSizeOfImage.height, 8, pixelSizeOfImage.width * 4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast);

  //draw image into context
  CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, pixelSizeOfImage.width, pixelSizeOfImage.height), image.CGImage);

  //get uniform of texture
  GLuint uniformIndex = glGetUniformLocation(__programPointer, [uniform UTF8String]);

  //generate texture
  GLuint textureIndex;
  glGenTextures(1, &textureIndex);
  glBindTexture(GL_TEXTURE_2D, textureIndex);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

  //create texture
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixelSizeOfImage.width, pixelSizeOfImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);

  glActiveTexture(GL_TEXTURE1);
  glBindTexture(GL_TEXTURE_2D, textureIndex);
  //"send" to shader
  glUniform1i(uniformIndex, 1); 

  free(spriteData);
  CGContextRelease(spriteContext);
}

纹理的统一很好，glGetUniformLocation函数不返回 -1。纹理是分辨率为 2000x2000 像素的 PNG 文件。

问题：当纹理传递给着色器时，我得到了“黑屏”。也许问题是CGContext的参数或函数glTexImage2D的参数

更新：我刚刚发现我需要将纹理单元编号传递给每个绘制周期，并且一切正常。真的有必要这样做吗？

谢谢

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