灰色图片

第一种实现

// 第一种
void HelloWorld::spriteToGrey(Sprite* sprite_chess)
{
    Point point = sprite_chess->getPosition();
    sprite_chess->setPosition(sprite_chess->getContentSize().width / 2, sprite_chess->getContentSize().height / 2);
    RenderTexture *render = RenderTexture::create(sprite_chess->getContentSize().width, sprite_chess->getContentSize().height, Texture2D::PixelFormat::RGBA8888);
    render->beginWithClear(0.0f, 0.0f, 0.0f, 0.0f);
    sprite_chess->visit();
    render->end();
    Director::getInstance()->getRenderer()->render();
    Image *finalImage = render->newImage();
    unsigned char *pData = finalImage->getData();
    int iIndex = 0;
    for (int i = 0; i < finalImage->getHeight(); i++)
    {
        for (int j = 0; j < finalImage->getWidth(); j++)
        {
            // gray
            int iBPos = iIndex;
            unsigned int iB = pData[iIndex];
            iIndex++;
            unsigned int iG = pData[iIndex];
            iIndex++;
            unsigned int iR = pData[iIndex];
            iIndex++;
            iIndex++;
            unsigned int iGray = 0.3 * iR + 0.6 * iG + 0.1 * iB;
            pData[iBPos] = pData[iBPos + 1] = pData[iBPos + 2] = (unsigned char)iGray;
        }
    }
    Texture2D *texture = new Texture2D;
    texture->initWithImage(finalImage);
    delete finalImage;
    sprite_chess->setTexture(texture);
    texture->release();
    sprite_chess->setPosition(point);
}

第二种实现 - 第二种实现较好

//实现Sprite或者ImageView类型的图片变灰（已修正位置偏移问题）
void HelloWorld::spriteToGrey2(Node* tempSp)
{
    ImageView* imgView = dynamic_cast<ImageView*>(tempSp);
    Sprite* imgView2 = dynamic_cast<Sprite*>(tempSp);
    Sprite* sp = nullptr;
    if (imgView) {
        Scale9Sprite* scale9sp = dynamic_cast<Scale9Sprite*>(imgView->getVirtualRenderer());
        if (scale9sp) {
            sp = scale9sp->getSprite();
        }
    }
    else if (imgView2) {
        sp = imgView2;
    }
    if (!sp) {
        return;
    }
    const GLchar* pszFragSource =
        "#ifdef GL_ES \n\
    precision mediump float; \n\
#endif \n\
    varying vec2 v_texCoord; \n\
    varying vec4 v_fragmentColor; \n\
    void main(void) \n\
    { \n\
        // Convert to greyscale using NTSC weightings \n\
        vec4 col = v_fragmentColor * texture2D(CC_Texture0, v_texCoord); \n\
        float grey = dot(col.rgb, vec3(0.299, 0.587, 0.114)); \n\
        gl_FragColor = vec4(grey, grey, grey, col.a); \n\
    }";
    GLProgram* pProgram = new GLProgram();
    pProgram->initWithByteArrays(ccPositionTextureColor_noMVP_vert, pszFragSource);
    sp->setGLProgram(pProgram);
    pProgram->release();
    CHECK_GL_ERROR_DEBUG();
    sp->getGLProgram()->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION);
    sp->getGLProgram()->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_COLOR, GLProgram::VERTEX_ATTRIB_COLOR);
    sp->getGLProgram()->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORD);
    CHECK_GL_ERROR_DEBUG();
    sp->getGLProgram()->link();
    CHECK_GL_ERROR_DEBUG();
    sp->getGLProgram()->updateUniforms();
    CHECK_GL_ERROR_DEBUG();
}

来自为知笔记(Wiz)