Cocos2d-x使用CCGLProgram和Shader文件实现精灵置灰

1. 实现方法：

CCGraySprite

 继承自 

CCSprite

 覆盖

initWithTexture

和

draw

方法实现置灰。
方法和属性声明：

class CCGraySprite : public CCSprite{
public:
CCGraySprite();
virtual ~CCGraySprite();
static CCGraySprite* create(const char* pszFileName);
bool initWithTexture(CCTexture2D* pTexture, const CCRect& tRect);
static CCGraySprite* createWithSprite(CCSprite *pSprite);
static CCGraySprite* createWithNodeAndItChild(CCNode *pNode);
void setGray(bool isGray);
virtual void draw();

private:
bool m_isGray;
CCGLProgram* pProgram;
};

m_isGray

 是否置灰

pProgram

 保存置灰的GL程序

2. shader字符串:

可以像官方那样写在一个.h文件中

GLchar* pszFragSource = (GLchar*)
"#ifdef GL_ES \n \
precision mediump float; \n \
#endif \n \
uniform sampler2D u_texture; \n \
varying vec2 v_texCoord; \n \
varying vec4 v_fragmentColor; \n \
void main(void) \n \
{ \n \
// Convert to greyscale using NTSC weightings \n \
vec4 col = texture2D(u_texture, v_texCoord); \n \
float grey = dot(col.rgb, vec3(0.299, 0.587, 0.114)); \n \
gl_FragColor = vec4(grey, grey, grey, col.a); \n \
}";

3. 核心代码：

覆盖父类的

initWithTexture

和

draw

方法，根据

m_isGray

调用对应GL程序进行渲染绘制精灵

void CCGraySprite::setGray(bool isGray) {
m_isGray = isGray;
if (isGray == true) {
this->setShaderProgram(pProgram);
}else
{
this->setShaderProgram(CCShaderCache::sharedShaderCache()->programForKey(kCCShader_PositionTextureColor));
}
}

bool CCGraySprite::initWithTexture(CCTexture2D* pTexture, const CCRect& tRect ){
m_isGray = true;
do{
CC_BREAK_IF(!CCSprite::initWithTexture(pTexture, tRect));

GLchar* pszFragSource = (GLchar*)
"#ifdef GL_ES \n \
precision mediump float; \n \
#endif \n \
uniform sampler2D u_texture; \n \
varying vec2 v_texCoord; \n \
varying vec4 v_fragmentColor; \n \
void main(void) \n \
{ \n \
// Convert to greyscale using NTSC weightings \n \
vec4 col = texture2D(u_texture, v_texCoord); \n \
float grey = dot(col.rgb, vec3(0.299, 0.587, 0.114)); \n \
gl_FragColor = vec4(grey, grey, grey, col.a); \n \
}";

pProgram = new CCGLProgram();
pProgram->initWithVertexShaderByteArray(ccPositionTextureColor_vert, pszFragSource);
this->setShaderProgram(pProgram);
CHECK_GL_ERROR_DEBUG();

this->getShaderProgram()->addAttribute(kCCAttributeNamePosition, kCCVertexAttrib_Position);
this->getShaderProgram()->addAttribute(kCCAttributeNameColor, kCCVertexAttrib_Color);
this->getShaderProgram()->addAttribute(kCCAttributeNameTexCoord, kCCVertexAttrib_TexCoords);
CHECK_GL_ERROR_DEBUG();

this->getShaderProgram()->link();
CHECK_GL_ERROR_DEBUG();

this->getShaderProgram()->updateUniforms();
CHECK_GL_ERROR_DEBUG();

return true;
} while (0);
return false;
}

void CCGraySprite::draw(){
if (this->getTexture() == NULL) {
return;
}
if(m_isGray == false){
CCSprite::draw();
return;
}

ccGLEnableVertexAttribs(kCCVertexAttribFlag_PosColorTex );
ccGLBlendFunc( m_sBlendFunc.src, m_sBlendFunc.dst );

this->getShaderProgram()->use();
this->getShaderProgram()->setUniformsForBuiltins();

ccGLBindTexture2D( this->getTexture()->getName() );

#define kQuadSize sizeof(m_sQuad.bl)
long offset = (long)&m_sQuad;

// vertex
int diff = offsetof( ccV3F_C4B_T2F, vertices);
glVertexAttribPointer(kCCVertexAttrib_Position, 3, GL_FLOAT, GL_FALSE, kQuadSize, (void*) (offset + diff));

// texCoods
diff = offsetof( ccV3F_C4B_T2F, texCoords);
glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, kQuadSize, (void*)(offset + diff));

// color
diff = offsetof( ccV3F_C4B_T2F, colors);
glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (void*)(offset + diff));
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
CC_INCREMENT_GL_DRAWS(1);
}

4. lua使用示例

需手写.pkg文件，使用tolua++工具导出Lua binding文件，在AppDelegate::applicationDidFinishLaunching()注册后，方可在lua层使用

local nameBgSp = CCGraySprite:create("images/namebg.png")

local normalSp = CCSprite:create("images/namebg.png")
local graySp = CCGraySprite:createWithNodeAndItChild(normalSp)

local frameSp = CCGraySprite:create("images/frame.png")
frameSp:setGray(isGray)

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