Opengl_under_qml第三弹----------------------纹理贴图（YUV）
本文接上文
Opengl_under_qml第三弹----------------------纹理贴图（YUV）
主要通过程序将yuv数据送给shader，通过gpu来转成rgb进而渲染。
与上文主要不同的地方还是paint函数，为了容易看懂，没有将其写成多个函数的形式，也没有加测试代码，
voidSquircleRenderer::paint()
{
//initializeGLFunctions();
initializeOpenGLFunctions();
if(!m_program){
m_program=newQOpenGLShaderProgram();
m_program->addShaderFromSourceCode(QOpenGLShader::Vertex,
"attributehighpvec4vertexIn;"
"attributehighpvec2textureIn;"
"varyingvec2textureOut;"
"voidmain(void){"
"gl_Position=vertexIn;"
"textureOut=textureIn;}");
m_program->addShaderFromSourceCode(QOpenGLShader::Fragment,
"varyingvec2textureOut;"
"uniformsampler2Dtex_y;"
"uniformsampler2Dtex_u;"
"uniformsampler2Dtex_v;"
"voidmain(void){"
"vec3yuv;"
"vec3rgb;"
"yuv.x=texture2D(tex_y,textureOut).r;"
"yuv.y=texture2D(tex_u,textureOut).r-0.5;"
"yuv.z=texture2D(tex_v,textureOut).r-0.5;"
"rgb=mat3(1,1,1,"
"0,-0.39465,
2.03211,"
"1.13983,-0.58060,0)*yuv;"
"gl_FragColor=vec4(rgb,1);}");
m_program->bindAttributeLocation("vertexIn",ATTRIB_VERTEX);
m_program->bindAttributeLocation("textureIn",ATTRIB_TEXTURE);
m_program->link();
}
m_program->bind();
staticconstGLfloatvertexVertices[]={
-1.0f,-1.0f,
1.0f,-1.0f,
-1.0f,1.0f,
1.0f,1.0f,
};
m_program->setAttributeArray(ATTRIB_VERTEX,GL_FLOAT,vertexVertices,2);
m_program->enableAttributeArray(ATTRIB_VERTEX);
staticconstGLfloattextureVertices[]={
0.0f,1.0f,
1.0f,1.0f,
0.0f,0.0f,
1.0f,0.0f,
};
m_program->setAttributeArray(ATTRIB_TEXTURE,GL_FLOAT,textureVertices,2);
m_program->enableAttributeArray(ATTRIB_TEXTURE);
GLuintTextureID0=m_program->uniformLocation("tex_y");
GLuintTextureID1=m_program->uniformLocation("tex_u");
GLuintTextureID2=m_program->uniformLocation("tex_v");
GLuintytexture,utexture,vtexture;
glGenTextures(1,&ytexture);
glBindTexture(GL_TEXTURE_2D,ytexture);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,(GLfloat)GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,(GLfloat)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);
glGenTextures(1,&utexture);
glBindTexture(GL_TEXTURE_2D,utexture);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,(GLfloat)GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,(GLfloat)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);
glGenTextures(1,&vtexture);
glBindTexture(GL_TEXTURE_2D,vtexture);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,(GLfloat)GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,(GLfloat)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);
FILE*fp;
if((fp=fopen("D:/testyuv.yuv","rb"))==NULL)
{
printf("cantopenthefile");
exit(0);
}
unsignedchardata[size];
fread(data,1,size,fp);
unsignedchar*y=data,*u=y+Pitch,*v=u+(Pitch>>2);//iePITCH*HEIGHT16*1/4
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,ytexture);
glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE,MAIN_TEXTURE_WIDTH,MAIN_TEXTURE_HEIGHT,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,y);
m_program->setUniformValue(TextureID0,0);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D,utexture);
glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE,MAIN_TEXTURE_WIDTH/2,MAIN_TEXTURE_HEIGHT/2,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,u);
m_program->setUniformValue(TextureID1,1);
glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D,vtexture);
glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE,MAIN_TEXTURE_WIDTH/2,MAIN_TEXTURE_HEIGHT/2,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,v);
m_program->setUniformValue(TextureID2,2);
glViewport(0,0,m_viewportSize.width(),m_viewportSize.height());
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_TRIANGLE_STRIP,0,4);
glDisable(GL_DEPTH_TEST);
m_program->disableAttributeArray(ATTRIB_VERTEX);
m_program->disableAttributeArray(ATTRIB_VERTEX);
fclose(fp);
m_program->release();
}
先看shader的代码：
首先Vsh：
attributehighpvec4vertexIn;
attributehighpvec2textureIn;
varyingvec2textureOut;
voidmain(void){
gl_Position=vertexIn;
textureOut=textureIn;
定义了两个attribute变量，一个作为顶点着色器的坐标vertexIn，另一个textureIn用于传给fsh的textureOut变量来进行纹理绘制，这里跟上一篇略有不同，原因是我参考的例子不同，应该使按照上一篇只定义一个坐标变量就行了，这里不再修改了。
然后是Fsh。
varyingvec2textureOut;
uniformsampler2Dtex_y;"
uniformsampler2Dtex_u;"
uniformsampler2Dtex_v;"
voidmain(void){"
vec3yuv;"
vec3rgb;"
yuv.x=texture2D(tex_y,textureOut).r;
yuv.y=texture2D(tex_u,textureOut).r-0.5;
yuv.z=texture2D(tex_v,textureOut).r-0.5;
rgb=mat3(1,1,1,
0,-0.39465,2.03211,
1.13983,-0.58060,0)*yuv;
gl_FragColor=vec4(rgb,1);}
textureOut是从vsh传递过来的用于绘制纹理的坐标变量，tex_y，tex_u，tex_v是定义的是纹理变量（sampler2D），然后把值给yuv，然后通过一个矩阵的乘法，得到rgb数据，这里和普通的yuv-转rgb是一样的，只不过是放在gpu转换。
具体的顶点坐标传值在上一篇文章里介绍了，这里就不在说了。主要说纹理的生成，（其实部分也是和上一篇文章是一样的，都是把buffer data传给sample2d纹理变量，这里把所有的东西（包括读取数据）写到一个流程里了）
GLuintytexture,utexture,vtexture;//定义纹理id
glGenTextures(1,&ytexture); //生成纹理
glBindTexture(GL_TEXTURE_2D,ytexture);//绑定纹理
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,(GLfloat)GL_LINEAR);//设置纹理参数
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,(GLfloat)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);
然后是读取文件操作：
//读取文件到fp
FILE*fp;
fp=fopen("D:/testyuv.yuv","rb")
//从fp读取数据到data，大小是size，个数是1
unsignedchardata[size];
fread(data,1,size,fp);
定义指针指向data数据
unsignedchar*y=data,*u=y+Pitch,*v=u+(Pitch>>2);//iePITCH*HEIGHT16*1/4
这里的对yuv数据加以说明，一帧分辨率为Pitch=imagewidth*imageheight的yuv数据，总共的数据量有3*Pitch/2个字节,其中y数据占Pitch个字节，所以程序里有:“*u = y + Pitch”,然后u数据，占Pitch/4个字节，所以程序里:”*v
= u + (Pitch >> 2)”，意思就是PITCH*HEIGHT16*1/4，最后v数据占Pitch/4个字节，
这里需要说明的是，文件一旦打开，及执行完
FILE*fp;
fp=fopen("D:/testyuv.yuv","rb")
第一次fread(data,1,size,fp);就是读取第一帧，在没有执行fclose的前提下，再执行一次fclose，那么就会读取的是下一帧，这个根文件操作有关，具体的就不知道了。
然后是纹理绑定数据
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,ytexture);
glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE,MAIN_TEXTURE_WIDTH,MAIN_TEXTURE_HEIGHT,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,y);
m_program->setUniformValue(TextureID0,0);
跟上一篇文章是一样的，只不过glTexImage2D变量不一样，上一篇是rgb三阶数据绑定到一个纹理变量中，所以第二个变量是GL_RGB，这里一次只绑定一阶数据，所以第二个变量设置成GL_LUMINANCE
还有要注意的是大小，对于y数据是MAIN_TEXTURE_WIDTH,MAIN_TEXTURE_HEIGHT，但是对于u和v数据就是MAIN_TEXTURE_WIDTH,MAIN_TEXTURE_HEIGHT/2,原因上边已经讲过了。
最后就是老一套绘图，
glViewport(0,0,m_viewportSize.width(),m_viewportSize.height());
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_TRIANGLE_STRIP,0,4);
glDisable(GL_DEPTH_TEST);
代码：http://download.csdn.net/detail/u010423298/8699493 | 
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