第11月第14天 opengl yuv
Posted lianhuaren
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1.
Here is some snippets of code from my project ‘movie player for ios‘.
1. fragment shader
varying highp vec2 v_texcoord;
uniform sampler2D s_texture_y;
uniform sampler2D s_texture_u;
uniform sampler2D s_texture_v;
void main() {
highp float y = texture2D(s_texture_y, v_texcoord).r;
highp float u = texture2D(s_texture_u, v_texcoord).r - 0.5;
highp float v = texture2D(s_texture_v, v_texcoord).r - 0.5;
highp float r = y + 1.402 * v;
highp float g = y - 0.344 * u - 0.714 * v;
highp float b = y + 1.772 * u;
gl_FragColor = vec4(r,g,b,1.0);
}
2. create textures from YUV420p frame
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(3, _textures);
const UInt8 *pixels[3] = { yuvFrame.luma.bytes, yuvFrame.chromaB.bytes, yuvFrame.chromaR.bytes };
const NSUInteger widths[3] = { frameWidth, frameWidth / 2, frameWidth / 2 };
const NSUInteger heights[3] = { frameHeight, frameHeight / 2, frameHeight / 2 };
for (int i = 0; i < 3; ++i) {
glBindTexture(GL_TEXTURE_2D, _textures[i]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, widths[i],heights[i],0,GL_LUMINANCE,GL_UNSIGNED_BYTE,pixels[i]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
}
3. init vertices and texture coords
static const GLfloat texCoords[] = { 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f };
static const GLfloat vertices[]= {-1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, 1.0f };
4. render frame
[EAGLContext setCurrentContext:_context];
glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer);
glViewport(0, 0, _backingWidth, _backingHeight);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(_program);
for (int i = 0; i < 3; ++i) {
glActiveTexture(GL_TEXTURE0 + i);
glBindTexture(GL_TEXTURE_2D, _textures[i]);
glUniform1i(_uniformSamplers[i], i);
}
glVertexAttribPointer(ATTRIBUTE_VERTEX, 2, GL_FLOAT, 0, 0, vertices);
glEnableVertexAttribArray(ATTRIBUTE_VERTEX);
glVertexAttribPointer(ATTRIBUTE_TEXCOORD, 2, GL_FLOAT, 0, 0, texCoords);
glEnableVertexAttribArray(ATTRIBUTE_TEXCOORD);
glBindRenderbuffer(GL_RENDERBUFFER, _renderbuffer);
[_context presentRenderbuffer:GL_RENDERBUFFER];
The link to project on github.
https://stackoverflow.com/questions/12428108/ios-how-to-draw-a-yuv-image-using-opengl
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