opengl shader 图片变灰及还原，使用自己的shader崩溃问题

本来采用更改图片像素点变灰，现在需要还原，便用shader，发现变灰和还原后悔改变图片的位置，于是又寻找解决办法~

变灰和还原的函数

void addGray(Sprite* sprite)  
{  
if(sprite)
{
GLProgram * p = new GLProgram();
p->initWithFilenames("gray.vsh", "gray.fsh");
p->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION);
p->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_COLOR, GLProgram::VERTEX_ATTRIB_COLOR);
p->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORDS);
p->link();
p->updateUniforms();
sprite->setShaderProgram(p);
}
} 

网上down的gray.vsh变灰后改变位置解决办法：CC_MVPMatrix 改为CC_PMatrix

void removeGray(Sprite* sprite)  
{  
CCGLProgram* p = CCShaderCache::sharedShaderCache()->programForKey(GLProgram::SHADER_NAME_POSITION_TEXTURE_COLOR_NO_MVP);
sprite->setShaderProgram(p);
}

还原本应该设置为GLProgram::SHADER_NAME_POSITION_TEXTURE_COLOR，但是有会发生位置改变~所以改为GLProgram::SHADER_NAME_POSITION_TEXTURE_COLOR_NO_MVP

使用自己的shader，会崩溃，解决办法：

std::string GLProgram::logForOpenGLObject(GLuint object, GLInfoFunction infoFunc, GLLogFunction logFunc) const
{
    std::string ret;
    GLint logLength = 0, charsWritten = 0;


    //infoFunc(object, GL_INFO_LOG_LENGTH, &logLength);        //这里就崩溃了~~  不知道为什么 
    glGetShaderiv(object, GL_INFO_LOG_LENGTH, &logLength);     //直接改成调用opengel函数， 
    if (logLength < 1)
        return "";


    char *logBytes = (char*)malloc(logLength);
    // logFunc(object, logLength, &charsWritten, logBytes); //同上
    glGetShaderInfoLog(object, logLength, &charsWritten, logBytes);
    ret = logBytes;


    free(logBytes);
    return ret;
}

文件：

gray.fsh:

varying vec4 v_fragmentColor; 
varying vec2 v_texCoord; 

void main() 
{
vec4 v_orColor = v_fragmentColor * texture2D(CC_Texture0, v_texCoord);
float gray = dot(v_orColor.rgb, vec3(0.299, 0.587, 0.114));
gl_FragColor = vec4(gray, gray, gray, v_orColor.a);
}

gray.vsh:
attribute vec4 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;

varying vec4 v_fragmentColor;
varying vec2 v_texCoord;

void main() 
{ 
    gl_Position = CC_PMatrix * a_position;
v_fragmentColor = a_color;
v_texCoord = a_texCoord;
}