【转】cocos2d-x游戏开发(十四)用shader使图片背景透明

转自：http://blog.csdn.net/dawn_moon/article/details/8631783

好吧，终于抽时间写这篇文章了。

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。

这里用shader处理了像素，使黑色背景透明，直接上代码

ShaderSprite.h

 1 #ifndef __TestShader__ShaderSprite__
 2 #define __TestShader__ShaderSprite__
 3
 4 #include "cocos2d.h"
 5 USING_NS_CC;
 6
 7 class ShaderSprite : public CCSprite {
 8
 9 public:
10     static ShaderSprite* create(const char* pszFileName);
11     virtual bool initWithTexture(CCTexture2D *pTexture, const CCRect& rect);
12     virtual void draw(void);
13 };
14
15 #endif /* defined(__TestShader__ShaderSprite__) */

ShaderSprite.cpp

  1 #include "ShaderSprite.h"
  2
  3 static CC_DLL const GLchar *transparentshader =
  4 #include "tansparentshader.h"
  5
  6 ShaderSprite* ShaderSprite::create(const char *pszFileName)
  7 {
  8     ShaderSprite *pRet = new ShaderSprite();
  9     if (pRet && pRet->initWithFile(pszFileName)) {
 10         pRet->autorelease();
 11         return pRet;
 12     }
 13     else
 14     {
 15         delete pRet;
 16         pRet = NULL;
 17         return NULL;
 18     }
 19 }
 20
 21 bool ShaderSprite::initWithTexture(CCTexture2D *pTexture, const CCRect& rect)
 22 {
 23     do{
 24 //        CCLog("override initWithTexture!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
 25         CC_BREAK_IF(!CCSprite::initWithTexture(pTexture, rect));
 26
 27         // 加载顶点着色器和片元着色器
 28         m_pShaderProgram = new  CCGLProgram();
 29         m_pShaderProgram ->initWithVertexShaderByteArray(ccPositionTextureA8Color_vert, transparentshader);
 30
 31         CHECK_GL_ERROR_DEBUG();
 32
 33         // 启用顶点着色器的attribute变量，坐标、纹理坐标、颜色
 34         m_pShaderProgram->addAttribute(kCCAttributeNamePosition, kCCVertexAttrib_Position);
 35         m_pShaderProgram->addAttribute(kCCAttributeNameColor, kCCVertexAttrib_Color);
 36         m_pShaderProgram->addAttribute(kCCAttributeNameTexCoord, kCCVertexAttrib_TexCoords);
 37
 38         CHECK_GL_ERROR_DEBUG();
 39
 40         // 自定义着色器链接
 41         m_pShaderProgram->link();
 42
 43         CHECK_GL_ERROR_DEBUG();
 44
 45         // 设置移动、缩放、旋转矩阵
 46         m_pShaderProgram->updateUniforms();
 47
 48         CHECK_GL_ERROR_DEBUG();
 49
 50         return true;
 51
 52     }while(0);
 53     return false;
 54 }
 55
 56 void ShaderSprite::draw(void)
 57 {
 58 //    CCLog("override draw!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
 59     CC_PROFILER_START_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
 60
 61     CCAssert(!m_pobBatchNode, "If CCSprite is being rendered by CCSpriteBatchNode, CCSprite#draw SHOULD NOT be called");
 62
 63     CC_NODE_DRAW_SETUP();
 64
 65     //
 66     // 启用attributes变量输入，顶点坐标，纹理坐标，颜色
 67     //
 68     ccGLEnableVertexAttribs( kCCVertexAttribFlag_PosColorTex );
 69     ccGLBlendFunc(m_sBlendFunc.src, m_sBlendFunc.dst);
 70
 71     m_pShaderProgram->use();
 72     m_pShaderProgram->setUniformsForBuiltins();
 73
 74     // 绑定纹理到纹理槽0
 75     ccGLBindTexture2D(m_pobTexture->getName());
 76
 77
 78
 79 #define kQuadSize sizeof(m_sQuad.bl)
 80     long offset = (long)&m_sQuad;
 81
 82     // vertex
 83     int diff = offsetof( ccV3F_C4B_T2F, vertices);
 84     glVertexAttribPointer(kCCVertexAttrib_Position, 3, GL_FLOAT, GL_FALSE, kQuadSize, (void*) (offset + diff));
 85
 86     // texCoods
 87     diff = offsetof( ccV3F_C4B_T2F, texCoords);
 88     glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, kQuadSize, (void*)(offset + diff));
 89
 90     // color
 91     diff = offsetof( ccV3F_C4B_T2F, colors);
 92     glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (void*)(offset + diff));
 93
 94
 95     glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 96
 97     CHECK_GL_ERROR_DEBUG();
 98
 99     CC_INCREMENT_GL_DRAWS(1);
100     CC_PROFILER_STOP_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
101 }

片段着色器代码

tansparentshader.h

 1 "                                                       \n\
 2 #ifdef GL_ES                                            \n 3 precision lowp float;                                   \n 4 #endif                                                  \n 5 varying vec4 v_fragmentColor;                           \n 6 varying vec2 v_texCoord;                                \n 7 uniform sampler2D u_texture;                            \n 8 void main()                                             \n 9 {                                                       \n10     float ratio=0.0;                                    \n11     vec4 texColor = texture2D(u_texture, v_texCoord);   \n12     ratio = texColor[0] > texColor[1]?(texColor[0] > texColor[2] ? texColor[0] : texColor[2]) :(texColor[1] > texColor[2]? texColor[1] : texColor[2]);                                      \n13 if (ratio != 0.0)                                          \n14 {                                                          \n15     texColor[0] = texColor[0] /  ratio;                    \n16     texColor[1] = texColor[1] /  ratio;                    \n17     texColor[2] = texColor[2] /  ratio;                    \n18     texColor[3] = ratio;                                   \n19 }                                                          \n20 else                                                       \n21 {                                                          \n22     texColor[3] = 0.0;                                     \n23 }                                                          \n24 gl_FragColor = v_fragmentColor*texColor;                   \n25 }";

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。

【转】cocos2d-x游戏开发(十四)用shader使图片背景透明