SDL2+OpenGL (4)混合图像产生动态效果

利用OpenGL的glBlendFunc函数将下面这张图作为纹理产生动态效果

 1  #include <GL/glew.h>
 2  #include <SDL2/SDL.h>
 3  #include <SDL2/SDL_opengl.h>
 4  #include <SDL2/SDL_image.h>
 5  bool quit;
 6  SDL_Window* window;
 7  SDL_GLContext glContext;
 8  SDL_Event sdlEvent;
 9  GLuint      texture;
10  float x=0,y=0;
11  void Init()
12  {
13      SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
14      SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
15      SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE,32);
16      SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
17      SDL_Init(SDL_INIT_EVERYTHING);
18      window = SDL_CreateWindow("SDL+OpenGL", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,600,600,SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN );
19      glContext = SDL_GL_CreateContext(window);
20      SDL_GL_SetSwapInterval(1);
21      glewInit();
22      glEnable(GL_TEXTURE_2D);
23      glClearDepth(1.0f);
24      glDepthFunc(GL_LEQUAL);
25      glEnable(GL_DEPTH_TEST);
26      glShadeModel(GL_SMOOTH);
27  }
28  void LoadImage()
29  {
30      SDL_Surface *tmp=IMG_Load("water.png");
31      tmp = SDL_ConvertSurfaceFormat(tmp,SDL_PIXELFORMAT_ABGR8888,0);
32      texture=gluBuild2DMipmaps(GL_TEXTURE_2D,4,tmp->w,tmp->h,GL_RGBA,GL_UNSIGNED_BYTE,tmp->pixels);
33      SDL_FreeSurface(tmp);
34  }
35  void Draw()
36  {
37      if(x>=5)  x=0;
38      if(y>=5)  y=0;
39      glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
40      glLoadIdentity();
41      glScaled(1.0f/10,1.0f/10,1.0f/10);
42
43      glPushMatrix();
44          glEnable(GL_BLEND);
45              glColor4f(1.0f,1.0f,1.0f,0.5f);
46              glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_CONSTANT_ALPHA);
47              glTranslatef(0.0f, 0.0f, 1.0f);
48              glBindTexture(GL_TEXTURE_2D,texture);
49              glBegin(GL_QUADS);
50                  glTexCoord2f(5.0f+x, 5.0f+y); glVertex3f(-10.0f,  10.0f,  0.0f);
51                  glTexCoord2f(5.0f+x, 0.0f+y); glVertex3f( 10.0f,  10.0f,  0.0f);
52                  glTexCoord2f(0.0f+x, 0.0f+y); glVertex3f( 10.0f, -10.0f,  0.0f);
53                  glTexCoord2f(0.0f+x, 5.0f+y); glVertex3f(-10.0f, -10.0f,  0.0f);
54              glEnd();
55          glDisable(GL_BLEND);
56      glPopMatrix();
57
58      glPushMatrix();
59          glEnable(GL_BLEND);
60              glColor4f(1.0f,1.0f,1.0f,0.6f);
61              glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_CONSTANT_ALPHA);
62              glTranslatef(0.0f, 0.0f, 0.0f);
63              glBindTexture(GL_TEXTURE_2D,texture);
64              glBegin(GL_QUADS);
65                  glTexCoord2f(5.0f-x, 5.0f-y); glVertex3f(-10.0f,  10.0f,  0.0f);
66                  glTexCoord2f(5.0f-x, -5.0f-y); glVertex3f( 10.0f,  10.0f,  0.0f);
67                  glTexCoord2f(0.0f-x, -5.0f-y); glVertex3f( 10.0f, -10.0f,  0.0f);
68                  glTexCoord2f(0.0f-x, 5.0f-y); glVertex3f(-10.0f, -10.0f,  0.0f);
69              glEnd();
70          glDisable(GL_BLEND);
71      glPopMatrix();
72
73      x+=0.005;
74      y+=0.005;
75      SDL_GL_SwapWindow(window);
76  }
77  int main(int argc, char *argv[])
78  {
79      quit = false;
80      Init();
81      LoadImage();
82      while (!quit)
83      {
84          while(SDL_PollEvent(&sdlEvent))
85          {
86              if(sdlEvent.type == SDL_QUIT)
87              {
88                  quit = true;
89              }
90          }
91          Draw();
92          SDL_Delay(16);
93      }
94      SDL_DestroyWindow(window);
95      window = NULL;
96      SDL_Quit();
97      return 0;
98  }

效果（gif文件录制的太短了，效果不是很明显）