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【转】cocos2d-x游戏开发(十四)用shader使图片背景透明

2024-07-10 03:47:39   220人阅读

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。

 

 


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