好吧，终于抽时间写这篇文章了。@H_404_2@

手头上有很多人物行走图，技能特效图等，但这些图都有个纯黑色背景，怎么样将内容显示出来，让背景透明呢？前段时间搞了一下，感谢群里的童鞋们，提供了思路和方法。@H_404_2@

@H_404_2@

这里用shader处理了像素，使黑色背景透明，直接上代码@H_404_2@

ShaderSprite.h@H_404_2@

#ifndef __TestShader__ShaderSprite__@H_404_2@
#define@H_404_2@ __TestShader__ShaderSprite__@H_404_2@

#include "cocos2d.h"@H_404_2@
USING_NS_CC;

class@H_404_2@ ShaderSprite : public@H_404_2@ CCSprite {
    
public@H_404_2@:
    static@H_404_2@ ShaderSprite* create(const@H_404_2@ char@H_404_2@* pszFileName);
    virtual@H_404_2@ bool@H_404_2@ initWithTexture(CCTexture2D *pTexture,const@H_404_2@ CCRect& rect);
    void@H_404_2@ draw(void@H_404_2@);
};

endif@H_404_2@ /* defined(__TestShader__ShaderSprite__) */@H_404_2@@H_404_2@

ShaderSprite.cpp@H_404_2@@H_404_2@

#include "ShaderSprite.h"@H_404_2@

static@H_404_2@ CC_DLL const@H_404_2@ GLchar *transparentshader =
#include "tansparentshader.h"@H_404_2@

ShaderSprite* ShaderSprite::create(char@H_404_2@ *pszFileName)
{
    ShaderSprite *pRet = new@H_404_2@ ShaderSprite();
    if@H_404_2@ (pRet && pRet->initWithFile(pszFileName)) {
        pRet->autorelease();
        return@H_404_2@ pRet;
    }
    else@H_404_2@
    {
        delete pRet;
        pRet = NULL;
        return@H_404_2@ NULL;
    }
}

bool@H_404_2@ ShaderSprite::initWithTexture(CCTexture2D *pTexture,51); font-weight:bold">const@H_404_2@ CCRect& rect)
{
    do@H_404_2@{
// CCLog("override initWithTexture!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");@H_404_2@
        CC_BREAK_IF(!CCSprite::initWithTexture(pTexture,rect));
        
        // 加载顶点着色器和片元着色器@H_404_2@
        m_pShaderProgram = new@H_404_2@  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@H_404_2@
        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@H_404_2@
        m_pShaderProgram->link();
        
        CHECK_GL_ERROR_DEBUG();
        
        // 设置移动、缩放、旋转矩阵@H_404_2@
        m_pShaderProgram->updateUniforms();
        
        CHECK_GL_ERROR_DEBUG();
        
        return@H_404_2@ true@H_404_2@;
        
    }while@H_404_2@(0@H_404_2@);
    false@H_404_2@;
}

void@H_404_2@ ShaderSprite::draw(void@H_404_2@)
{
// CCLog("override draw!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");@H_404_2@
    CC_PROFILER_START_CATEGORY(kCCProfilerCategorySprite,"CCSprite - draw"@H_404_2@);
    
    CCAssert(!m_pobBatchNode,68)">"If CCSprite is being rendered by CCSpriteBatchNode,CCSprite#draw SHOULD NOT be called"@H_404_2@);
    
    CC_NODE_DRAW_SETUP();
    
    //@H_404_2@
// 启用attributes变量输入，顶点坐标，纹理坐标，颜色@H_404_2@
//@H_404_2@
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@H_404_2@
    ccGLBindTexture2D(m_pobTexture->getName());


    
define@H_404_2@ kQuadSize sizeof(m_sQuad.bl)@H_404_2@
long@H_404_2@ offset = (long@H_404_2@)&m_sQuad;
    
// vertex@H_404_2@
int@H_404_2@ diff = offsetof( ccV3F_C4B_T2F,vertices);
glVertexAttribPointer(kCCVertexAttrib_Position,3@H_404_2@,GL_FLOAT,GL_FALSE,kQuadSize,(void@H_404_2@*) (offset + diff));
    
// texCoods@H_404_2@
diff = offsetof( ccV3F_C4B_T2F,texCoords);
glVertexAttribPointer(kCCVertexAttrib_TexCoords,153)">2@H_404_2@,51); font-weight:bold">void@H_404_2@*)(offset + diff));
    
// color@H_404_2@
diff = offsetof( ccV3F_C4B_T2F,colors);
glVertexAttribPointer(kCCVertexAttrib_Color,153)">4@H_404_2@,GL_UNSIGNED_BYTE,GL_TRUE,51); font-weight:bold">void@H_404_2@*)(offset + diff));
    
    
glDrawArrays(GL_TRIANGLE_STRIP,153)">0@H_404_2@,153)">4@H_404_2@);
    
CHECK_GL_ERROR_DEBUG();

    CC_INCREMENT_GL_DRAWS(1@H_404_2@);
    CC_PROFILER_STOP_CATEGORY(kCCProfilerCategorySprite,68)">"CCSprite - draw"@H_404_2@);
}@H_404_2@

片段着色器代码@H_404_2@@H_404_2@

tansparentshader.h@H_404_2@

" \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@H_404_2@; \n\ }"@H_404_2@;@H_404_2@

注意shader编程没有隐士数据类型转换，所以都显示为float了。@H_404_2@@H_404_2@

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。@H_404_2@

上图：@H_404_2@

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。@H_404_2@