cocos2d-x—使用shader使图片背景透明

这里用shader处理了像素，使黑色背景透明，直接上代码

ShaderSprite.h

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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

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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.         // 载入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.         // 自己定义着色器链接  
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

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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. {                                                       \n\  
10.     float ratio=0.0;                                    \n\  
11.     vec4 texColor = texture2D(u_texture, v_texCoord);   \n\  
12.     ratio = texColor[0] > texColor[1]?(texColor[0] > texColor[2] ? texColor[0] : texColor[2]) :(texColor[1] > texColor[2]? texColor[1] : texColor[2]);                                      \n\  
13. if (ratio != 0.0)                                          \n\  
14. {                                                          \n\  
15.     texColor[0] = texColor[0] /  ratio;                    \n\  
16.     texColor[1] = texColor[1] /  ratio;                    \n\  
17.     texColor[2] = texColor[2] /  ratio;                    \n\  
18.     texColor[3] = ratio;                                   \n\  
19. }                                                          \n\  
20. else                                                       \n\  
21. {                                                          \n\  
22.     texColor[3] = 0.0;                                     \n\  
23. }                                                          \n\  
24. gl_FragColor = v_fragmentColor*texColor;                   \n\  
25. }";  

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，假设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。仅仅是屏幕背景一个是白色，一个是黑色。图片背景透明了。

来源：https://www.cnblogs.com/hrhguanli/p/4480883.html