sdl实现texture透明

 sdl可以实现一些图片，文字透明，实现renderer透明。这里说的是texture透明，关于其他透明函数，请查看：点击打开链接

  如果闪退，尝试更改字体路径。

  效果图：

  代码：

#include <SDL2/SDL.h>#include <SDL2/SDL_ttf.h>//显示的texture的数量const int TexNum =3;SDL_Window*window=NULL;SDL_Renderer*renderer=NULL;//窗口类class Window{    public:    //记录是否加载成功    bool load;    //构造函数    Window(char title[20], Uint32 w=720, Uint32 h=1280, int flag=0)   {        load=false;        if (!SDL_Init(SDL_INIT_VIDEO))        if (window=SDL_CreateWindow(title, 0, 0, w, h, flag))        if (renderer=SDL_CreateRenderer(window, -1, 0))        {            //加载窗口成功            load=true;        }    }        //析构函数    ~Window()    {SDL_DestroyRenderer(renderer);SDL_DestroyWindow(window);SDL_Quit();    }    //填充窗口：白色    void fullWindow()    {SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);SDL_RenderFillRect(renderer, NULL);    }    //刷新窗口    void reflush()    {SDL_RenderPresent(renderer);SDL_RenderClear(renderer);    }};//文字类class Font{    public:    TTF_Font*font;     //构造函数:size为字体大小    Font(int size=70)    {        TTF_Init();font=TTF_OpenFont("./resource/DroidSansFallback.ttf", size);    }    //析构函数    ~Font()    {        TTF_CloseFont(font);        font=0;        TTF_Quit();    }    //把文字加载成textureSDL_Texture*loadTex(char*str, int type=4)    {        switch (type)        {            case 0:TTF_SetFontStyle(font,TTF_STYLE_BOLD);break; //粗体            case 1:TTF_SetFontStyle(font,TTF_STYLE_ITALIC);break; //斜体            case 2:TTF_SetFontStyle(font,TTF_STYLE_UNDERLINE);break; //下划线            case 3:TTF_SetFontStyle(font,TTF_STYLE_STRIKETHROUGH);break; //删除线            case 4:TTF_SetFontStyle(font,TTF_STYLE_NORMAL);break; //正常        }        //文字颜色：黑色        SDL_Color color={0, 0, 0, 255};        SDL_Surface*surface=TTF_RenderUTF8_Blended(font, str, color);SDL_Texture*texture=SDL_CreateTextureFromSurface(renderer, surface);SDL_FreeSurface(surface);        return texture;    }};//纹理类class Tex{    public:    SDL_Texture*tex[TexNum];    SDL_Rect box[TexNum];    Font font;    //特效texture    SDL_Texture*texture;    SDL_Rect TexBox;    Uint8 alpha=255;    //构造函数    Tex()    {        char *str[TexNum]={"逐渐透明", "逐渐显现", "退出"};         for (int i=0; i<TexNum; i++)        {tex[i]=font.loadTex(str[i]);        int w,h;//获取纹理大小        SDL_QueryTexture(tex[i], NULL, NULL, &w, &h);//设置纹理的大小        box[i].w=w;        box[i].h=h;        }//设置纹理的坐标        box[0].x=50;        box[0].y=800;        box[1].x=400;        box[1].y=800;        box[2].x=270;        box[2].y=950;//设置特效textureFont BigFont(150);texture=BigFont.loadTex("texture");        int w,h;//获取纹理大小        SDL_QueryTexture(texture, NULL, NULL, &w, &h);TexBox.w=w;TexBox.h=h;    }    //析构函数    ~Tex()    {        for (int i=0; i<TexNum; i++)        {            if (tex[i]!=NULL)       SDL_DestroyTexture(tex[i]);        }SDL_DestroyTexture(texture);    }    //显示tex    void showTex(int n)    {SDL_RenderCopy(renderer, tex[n], NULL, &box[n]);    }//显示特效texturevoid showTexture(int x=100, int y=250){TexBox.x=x;     TexBox.y=y;SDL_SetTextureBlendMode(texture,SDL_BLENDMODE_BLEND);//设置texture透明度模式SDL_SetTextureAlphaMod(texture,alpha);//设置texture透明度SDL_RenderCopy(renderer, texture, NULL, &TexBox);}};//按钮类class Button{    SDL_Event event;    SDL_Rect box[TexNum];    //屏幕分辨率    int win_w,win_h;public :Tex tex;int m=-1; //按下和移动时按钮索引int n=-1;  //抬起时按钮索引//构造函数Button(){//获取屏幕分辨率SDL_GetWindowSize(window, &win_w, &win_h);//获取tex文字大小和坐标for (int i=0; i<TexNum; i++){box[i].x=tex.box[i].x;box[i].y=tex.box[i].y;box[i].w=tex.box[i].w;box[i].h=tex.box[i].h;}}void touch(){while (SDL_PollEvent(&event)){switch (event.type){//手指按下case SDL_FINGERDOWN://手指滑动case SDL_FINGERMOTION:{//event.tfinger.x和event.tfinger.y值范围：0~1SDL_Point point={event.tfinger.x*win_w, event.tfinger.y*win_h};for (int i=0; i<TexNum; i++)//判断触点是否在box矩形中中if (SDL_PointInRect(&point, &box[i]))m=i;}break;//手指抬起case SDL_FINGERUP:{//event.tfinger.x和event.tfinger.y值范围：0~1SDL_Point point={event.tfinger.x*win_w, event.tfinger.y*win_h};for (int i=0; i<TexNum; i++)//判断触点是否在box矩形中if (SDL_PointInRect(&point, &box[i]))n=i;m=-1;}break;}}}void show(){//绘画填充矩形for (int i=0; i<TexNum; i++){SDL_SetRenderDrawColor(renderer, 0, 255, 255, 0);SDL_RenderFillRect(renderer, &box[i]);}if (m!=-1){SDL_SetRenderDrawColor(renderer, 255, 0, 0, 0);SDL_RenderFillRect(renderer, &box[m]);}//显示文字for (int i=0; i<TexNum; i++)tex.showTex(i);}};//主函数int main(int argc, char**argv){    Window win("多个按钮");    Button button;    while (win.load)    {    button.touch();    button.show();    switch (button.n)    {    case -1:{button.tex.showTexture();    }break;    case 0:{if (button.tex.alpha>0)  //alpha值在0~255，要限制一下button.tex.alpha--;button.tex.showTexture();    }break;    case 1:{if (button.tex.alpha<255)button.tex.alpha++;button.tex.showTexture();    }break;    case 2:{    win.load=false;    }break;