这里用shader处理了像素，使黑色背景透明，直接上代码
ShaderSprite.h
- #ifndef __TestShader__ShaderSprite__
- #define __TestShader__ShaderSprite__
- #include "cocos2d.h"
- USING_NS_CC;
- class ShaderSprite : public CCSprite {
- public:
- static ShaderSprite* create(const char* pszFileName);
- virtual bool initWithTexture(CCTexture2D *pTexture, const CCRect& rect);
- virtual void draw(void);
- };
- #endif /* defined(__TestShader__ShaderSprite__) */
ShaderSprite.cpp
- #include "ShaderSprite.h"
- static CC_DLL const GLchar *transparentshader =
- #include "tansparentshader.h"
- ShaderSprite* ShaderSprite::create(const char *pszFileName)
- {
- ShaderSprite *pRet = new ShaderSprite();
- if (pRet && pRet->initWithFile(pszFileName)) {
- pRet->autorelease();
- return pRet;
- }
- else
- {
- delete pRet;
- pRet = NULL;
- return NULL;
- }
- }
- bool ShaderSprite::initWithTexture(CCTexture2D *pTexture, const CCRect& rect)
- {
- do{
- // CCLog("override initWithTexture!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
- CC_BREAK_IF(!CCSprite::initWithTexture(pTexture, rect));
- // 加载顶点着色器和片元着色器
- m_pShaderProgram = new CCGLProgram();
- m_pShaderProgram ->initWithVertexShaderByteArray(ccPositionTextureA8Color_vert, transparentshader);
- CHECK_GL_ERROR_DEBUG();
- // 启用顶点着色器的attribute变量，坐标、纹理坐标、颜色
- m_pShaderProgram->addAttribute(kCCAttributeNamePosition, kCCVertexAttrib_Position);
- m_pShaderProgram->addAttribute(kCCAttributeNameColor, kCCVertexAttrib_Color);
- m_pShaderProgram->addAttribute(kCCAttributeNameTexCoord, kCCVertexAttrib_TexCoords);
- CHECK_GL_ERROR_DEBUG();
- // 自定义着色器链接
- m_pShaderProgram->link();
- CHECK_GL_ERROR_DEBUG();
- // 设置移动、缩放、旋转矩阵
- m_pShaderProgram->updateUniforms();
- CHECK_GL_ERROR_DEBUG();
- return true;
- }while(0);
- return false;
- }
- void ShaderSprite::draw(void)
- {
- // CCLog("override draw!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
- CC_PROFILER_START_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
- CCAssert(!m_pobBatchNode, "If CCSprite is being rendered by CCSpriteBatchNode, CCSprite#draw SHOULD NOT be called");
- CC_NODE_DRAW_SETUP();
- //
- // 启用attributes变量输入，顶点坐标，纹理坐标，颜色
- //
- ccGLEnableVertexAttribs( kCCVertexAttribFlag_PosColorTex );
- ccGLBlendFunc(m_sBlendFunc.src, m_sBlendFunc.dst);
- m_pShaderProgram->use();
- m_pShaderProgram->setUniformsForBuiltins();
- // 绑定纹理到纹理槽0
- ccGLBindTexture2D(m_pobTexture->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);
- CHECK_GL_ERROR_DEBUG();
- CC_INCREMENT_GL_DRAWS(1);
- CC_PROFILER_STOP_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
- }
片段着色器代码
tansparentshader.h
- " \n\
- #ifdef GL_ES \n\
- precision lowp float; \n\
- #endif \n\
- varying vec4 v_fragmentColor; \n\
- varying vec2 v_texCoord; \n\
- uniform sampler2D u_texture; \n\
- void main() \n\
- { \n\
- float ratio=0.0; \n\
- vec4 texColor = texture2D(u_texture, v_texCoord); \n\
- ratio = texColor[0] > texColor[1]?(texColor[0] > texColor[2] ? texColor[0] : texColor[2]) :(texColor[1] > texColor[2]? texColor[1] : texColor[2]); \n\
- if (ratio != 0.0) \n\
- { \n\
- texColor[0] = texColor[0] / ratio; \n\
- texColor[1] = texColor[1] / ratio; \n\
- texColor[2] = texColor[2] / ratio; \n\
- texColor[3] = ratio; \n\
- } \n\
- else \n\
- { \n\
- texColor[3] = 0.0; \n\
- } \n\
- gl_FragColor = v_fragmentColor*texColor; \n\
- }";
注意shader编程没有隐士数据类型转换，所以都显示为float了。
然后ratio是指在rgb中找最大的，如果ratio为0直接将alpha设为0，否则alpha设为ratio，然后各rgb除以ratio，这里是为了做渐变，否则变化太生硬。
上图：
好了，上面两张图是一样的。只是屏幕背景一个是白色，一个是黑色。图片背景透明了。
