我试图在iPhone 4上的iOS 4.3中将原生平面图像渲染为OpenGL ES 2.0纹理.然而,纹理全部变黑.我的相机配置如下：
[videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange]
forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
我将像素数据传递给我的纹理,如下所示：
glTexImage2D(GL_TEXTURE_2D,GL_RGBA,bufferWidth,bufferHeight,GL_RGB_422_APPLE,GL_UNSIGNED_SHORT_8_8_REV_APPLE,CVPixelBufferGetBaseAddress(cameraFrame));
我的fragement着色器是：
varying highp vec2 textureCoordinate;
uniform sampler2D videoFrame;
void main() {
lowp vec4 color;
color = texture2D(videoFrame,textureCoordinate);
lowp vec3 convertedColor = vec3(-0.87075,0.52975,-1.08175);
convertedColor += 1.164 * color.g; // Y
convertedColor += vec3(0.0,-0.391,2.018) * color.b; // U
convertedColor += vec3(1.596,-0.813,0.0) * color.r; // V
gl_FragColor = vec4(convertedColor,1.0);
}
我的顶点着色器是
attribute vec4 position;
attribute vec4 inputTextureCoordinate;
varying vec2 textureCoordinate;
void main()
{
gl_Position = position;
textureCoordinate = inputTextureCoordinate.xy;
}
当我使用BGRA图像时,这很好用,而我的片段着色器只能这样做
gl_FragColor = texture2D(videoFrame,textureCoordinate);
如果我在这里遗失了什么？谢谢！
解决方法
好.我们在这里取得了成功.关键是将Y和UV作为两个单独的纹理传递给片段着色器.这是最终的着色器：
#ifdef GL_ES
precision mediump float;
#endif
varying vec2 textureCoordinate;
uniform sampler2D videoFrame;
uniform sampler2D videoFrameUV;
const mat3 yuv2rgb = mat3(
1,1.2802,1,-0.214821,-0.380589,2.127982,0
);
void main() {
vec3 yuv = vec3(
1.1643 * (texture2D(videoFrame,textureCoordinate).r - 0.0625),texture2D(videoFrameUV,textureCoordinate).r - 0.5,textureCoordinate).a - 0.5
);
vec3 rgb = yuv * yuv2rgb;
gl_FragColor = vec4(rgb,1.0);
}
你需要像这样创建纹理：
int bufferHeight = CVPixelBufferGetHeight(cameraFrame); int bufferWidth = CVPixelBufferGetWidth(cameraFrame); glBindTexture(GL_TEXTURE_2D,videoFrameTexture); glTexImage2D(GL_TEXTURE_2D,GL_LUMINANCE,GL_UNSIGNED_BYTE,CVPixelBufferGetBaseAddressOfPlane(cameraFrame,0)); glBindTexture(GL_TEXTURE_2D,videoFrameTextureUV); glTexImage2D(GL_TEXTURE_2D,GL_LUMINANCE_ALPHA,bufferWidth/2,bufferHeight/2,1));
然后像这样传递它们：
glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D,videoFrameTexture); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D,videoFrameTextureUV); glActiveTexture(GL_TEXTURE0); glUniform1i(videoFrameUniform,0); glUniform1i(videoFrameUniformUV,1);
男孩,我松了一口气！
附： yuv2rgb矩阵的值来自这里http://en.wikipedia.org/wiki/YUV,我从这里复制代码http://www.ogre3d.org/forums/viewtopic.php?f=5&t=25877,以找出如何获得正确的YUV值.
