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
#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。