SDL2源代码分析4：纹理（SDL_Texture）

一时失言乱红尘 2022-08-20 05:23 214阅读 0赞

=====================================================

SDL源代码分析系列文章列表：

[SDL2源代码分析1：初始化（SDL\_Init()）][SDL2_1_SDL_Init]

[SDL2源代码分析2：窗口（SDL\_Window）][SDL2_2_SDL_Window]

[SDL2源代码分析3：渲染器（SDL\_Renderer）][SDL2_3_SDL_Renderer]

[SDL2源代码分析4：纹理（SDL\_Texture）][SDL2_4_SDL_Texture]

[SDL2源代码分析5：更新纹理（SDL\_UpdateTexture()）][SDL2_5_SDL_UpdateTexture]

[SDL2源代码分析6：复制到渲染器（SDL\_RenderCopy()）][SDL2_6_SDL_RenderCopy]

[SDL2源代码分析7：显示（SDL\_RenderPresent()）][SDL2_7_SDL_RenderPresent]

[SDL2源代码分析8：视频显示总结][SDL2_8]

=====================================================

上一篇文章分析了SDL中创建渲染器的函数SDL\_CreateRenderer()。这篇文章继续分析SDL的源代码。本文分析SDL的纹理（SDL\_Texture）。

![20141103164709706][]

SDL播放视频的代码流程如下所示。  
初始化:

> SDL\_Init(): 初始化SDL。  
> SDL\_CreateWindow(): 创建窗口（Window）。  
> SDL\_CreateRenderer(): 基于窗口创建渲染器（Render）。  
> SDL\_CreateTexture(): 创建纹理（Texture）。

循环渲染数据:

> SDL\_UpdateTexture(): 设置纹理的数据。  
> SDL\_RenderCopy(): 纹理复制给渲染器。  
> 
> 
> SDL\_RenderPresent(): 显示。

上篇文章分析了该流程中的第3个函数SDL\_CreateRenderer()。本文继续分析该流程中的第4个函数SDL\_CreateTexture()。

## SDL\_Texture ##

SDL\_Texture结构定义了一个SDL中的纹理。如果直接使用SDL2编译好的SDK的话，是看不到SDL\_Texture的内部结构的。有关它的定义在头文件中只有一行代码，如下所示。

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1.  /\*\*
2.   \* \\brief An efficient driver-specific representation of pixel data
3.   \*/
4.  **struct** SDL\_Texture; 
5.  **typedef****struct** SDL\_Texture SDL\_Texture;

在源代码工程中可以看到SDL\_Texture的定义，位于render\\SDL\_sysrender.h文件中。它的定义如下。

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1.  /\* Define the SDL texture structure \*/
2.  **struct** SDL\_Texture 
3.  \{ 
4.  **const****void** \*magic; 
5.   Uint32 format; /\*\*< The pixel format of the texture \*/
6.  **int** access; /\*\*< SDL\_TextureAccess \*/
7.  **int** w; /\*\*< The width of the texture \*/
8.  **int** h; /\*\*< The height of the texture \*/
9.  **int** modMode; /\*\*< The texture modulation mode \*/
10.  SDL\_BlendMode blendMode; /\*\*< The texture blend mode \*/
11.  Uint8 r, g, b, a; /\*\*< Texture modulation values \*/
12. 
13. 
14.  SDL\_Renderer \*renderer; 
15. 
16. 
17. /\* Support for formats not supported directly by the renderer \*/
18.  SDL\_Texture \*native; 
19.  SDL\_SW\_YUVTexture \*yuv; 
20. **void** \*pixels; 
21. **int** pitch; 
22.  SDL\_Rect locked\_rect; 
23. 
24. 
25. **void** \*driverdata; /\*\*< Driver specific texture representation \*/
26. 
27. 
28.  SDL\_Texture \*prev; 
29.  SDL\_Texture \*next; 
30. \};

可以看出其中包含了一个“纹理”所具备的各种属性。下面来看看如何创建这个SDL\_Texture。

## SDL\_CreateTexture() ##

### **函数简介** ###

使用SDL\_CreateTexture()基于渲染器创建一个纹理。SDL\_CreateTexture()的原型如下。

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1.  SDL\_Texture \* SDLCALL SDL\_CreateTexture(SDL\_Renderer \* renderer, 
2.   Uint32 format, 
3.  **int** access, **int** w, 
4.  **int** h);

参数的含义如下。

renderer：目标渲染器。

format  ：纹理的格式。后面会详述。

access：可以取以下值（定义位于SDL\_TextureAccess中）

SDL\_TEXTUREACCESS\_STATIC  ：变化极少  
 SDL\_TEXTUREACCESS\_STREAMING  ：变化频繁

SDL\_TEXTUREACCESS\_TARGET：暂时没有理解

w：纹理的宽

h：纹理的高

创建成功则返回纹理的ID，失败返回0。

### **函数调用关系图** ###

SDL\_ CreateTexture ()关键函数的调用关系可以用下图表示。

[![SouthEast][]][SouthEast 1]

上面的图片不太清晰，更清晰的图片上传到了相册里面：

[http://my.csdn.net/leixiaohua1020/album/detail/1793543][SouthEast 1]

把相册里面的图片保存下来就可以得到清晰的图片了。

### **源代码分析** ###

SDL\_CreateTexture()的源代码位于render\\SDL\_render.c中。如下所示。

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1.  SDL\_Texture \* SDL\_CreateTexture(SDL\_Renderer \* renderer, Uint32 format, **int** access, **int** w, **int** h) 
2.  \{ 
3.   SDL\_Texture \*texture; 
4.  
5.  
6.   CHECK\_RENDERER\_MAGIC(renderer, NULL); 
7.  
8.  
9.  **if** (!format) \{ 
10.  format = renderer->info.texture\_formats\[0\]; 
11.  \} 
12. **if** (SDL\_ISPIXELFORMAT\_INDEXED(format)) \{ 
13.  SDL\_SetError("Palettized textures are not supported"); 
14. **return** NULL; 
15.  \} 
16. **if** (w <= 0 || h <= 0) \{ 
17.  SDL\_SetError("Texture dimensions can't be 0"); 
18. **return** NULL; 
19.  \} 
20. **if** ((renderer->info.max\_texture\_width && w > renderer->info.max\_texture\_width) || 
21.  (renderer->info.max\_texture\_height && h > renderer->info.max\_texture\_height)) \{ 
22.  SDL\_SetError("Texture dimensions are limited to %dx%d", renderer->info.max\_texture\_width, renderer->info.max\_texture\_height); 
23. **return** NULL; 
24.  \} 
25.  texture = (SDL\_Texture \*) SDL\_calloc(1, **sizeof**(\*texture)); 
26. **if** (!texture) \{ 
27.  SDL\_OutOfMemory(); 
28. **return** NULL; 
29.  \} 
30.  texture->magic = &texture\_magic; 
31.  texture->format = format; 
32.  texture->access = access; 
33.  texture->w = w; 
34.  texture->h = h; 
35.  texture->r = 255; 
36.  texture->g = 255; 
37.  texture->b = 255; 
38.  texture->a = 255; 
39.  texture->renderer = renderer; 
40.  texture->next = renderer->textures; 
41. **if** (renderer->textures) \{ 
42.  renderer->textures->prev = texture; 
43.  \} 
44.  renderer->textures = texture; 
45. 
46. 
47. **if** (IsSupportedFormat(renderer, format)) \{ 
48. **if** (renderer->CreateTexture(renderer, texture) < 0) \{ 
49.  SDL\_DestroyTexture(texture); 
50. **return** 0; 
51.  \} 
52.  \} **else** \{ 
53.  texture->native = SDL\_CreateTexture(renderer, 
54.  GetClosestSupportedFormat(renderer, format), 
55.  access, w, h); 
56. **if** (!texture->native) \{ 
57.  SDL\_DestroyTexture(texture); 
58. **return** NULL; 
59.  \} 
60. 
61. 
62. /\* Swap textures to have texture before texture->native in the list \*/
63.  texture->native->next = texture->next; 
64. **if** (texture->native->next) \{ 
65.  texture->native->next->prev = texture->native; 
66.  \} 
67.  texture->prev = texture->native->prev; 
68. **if** (texture->prev) \{ 
69.  texture->prev->next = texture; 
70.  \} 
71.  texture->native->prev = texture; 
72.  texture->next = texture->native; 
73.  renderer->textures = texture; 
74. 
75. 
76. **if** (SDL\_ISPIXELFORMAT\_FOURCC(texture->format)) \{ 
77.  texture->yuv = SDL\_SW\_CreateYUVTexture(format, w, h); 
78. **if** (!texture->yuv) \{ 
79.  SDL\_DestroyTexture(texture); 
80. **return** NULL; 
81.  \} 
82.  \} **else****if** (access == SDL\_TEXTUREACCESS\_STREAMING) \{ 
83. /\* The pitch is 4 byte aligned \*/
84.  texture->pitch = (((w \* SDL\_BYTESPERPIXEL(format)) + 3) & ~3); 
85.  texture->pixels = SDL\_calloc(1, texture->pitch \* h); 
86. **if** (!texture->pixels) \{ 
87.  SDL\_DestroyTexture(texture); 
88. **return** NULL; 
89.  \} 
90.  \} 
91.  \} 
92. **return** texture; 
93. \}

从源代码中可以看出，SDL\_CreateTexture()的大致流程如下。

**1.检查输入参数的合理性。**例如像素格式是否支持，宽和高是否小于等于0等等。

**2.新建一个SDL\_Texture。**调用SDL\_calloc()（实际上就是calloc()）为新建的SDL\_Texture分配内存。

**3.调用SDL\_Render的CreateTexture()方法创建纹理。**这一步是整个函数的核心。

下面我们详细看一下几种不同的渲染器的CreateTexture()的方法。

#### 1.Direct3D ####

Direct3D 渲染器中对应CreateTexture()的函数是D3D\_CreateTexture()，它的源代码如下所示（位于render\\direct3d\\SDL\_render\_d3d.c）。

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1.  **static****int** D3D\_CreateTexture(SDL\_Renderer \* renderer, SDL\_Texture \* texture) 
2.  \{ 
3.   D3D\_RenderData \*renderdata = (D3D\_RenderData \*) renderer->driverdata; 
4.   D3D\_TextureData \*data; 
5.   D3DPOOL pool; 
6.  **DWORD** usage; 
7.  **HRESULT** result; 
8.  
9.  
10.  data = (D3D\_TextureData \*) SDL\_calloc(1, **sizeof**(\*data)); 
11. **if** (!data) \{ 
12. **return** SDL\_OutOfMemory(); 
13.  \} 
14.  data->scaleMode = GetScaleQuality(); 
15. 
16. 
17.  texture->driverdata = data; 
18. 
19. 
20. \#ifdef USE\_DYNAMIC\_TEXTURE
21. **if** (texture->access == SDL\_TEXTUREACCESS\_STREAMING) \{ 
22.  pool = D3DPOOL\_DEFAULT; 
23.  usage = D3DUSAGE\_DYNAMIC; 
24.  \} **else**
25. \#endif
26. **if** (texture->access == SDL\_TEXTUREACCESS\_TARGET) \{ 
27. /\* D3DPOOL\_MANAGED does not work with D3DUSAGE\_RENDERTARGET \*/
28.  pool = D3DPOOL\_DEFAULT; 
29.  usage = D3DUSAGE\_RENDERTARGET; 
30.  \} **else** \{ 
31.  pool = D3DPOOL\_MANAGED; 
32.  usage = 0; 
33.  \} 
34. 
35. 
36.  result = 
37.  IDirect3DDevice9\_CreateTexture(renderdata->device, texture->w, 
38.  texture->h, 1, usage, 
39.  PixelFormatToD3DFMT(texture->format), 
40.  pool, &data->texture, NULL); 
41. **if** (FAILED(result)) \{ 
42. **return** D3D\_SetError("CreateTexture()", result); 
43.  \} 
44. 
45. 
46. **if** (texture->format == SDL\_PIXELFORMAT\_YV12 || 
47.  texture->format == SDL\_PIXELFORMAT\_IYUV) \{ 
48.  data->yuv = SDL\_TRUE; 
49. 
50. 
51.  result = 
52.  IDirect3DDevice9\_CreateTexture(renderdata->device, texture->w / 2, 
53.  texture->h / 2, 1, usage, 
54.  PixelFormatToD3DFMT(texture->format), 
55.  pool, &data->utexture, NULL); 
56. **if** (FAILED(result)) \{ 
57. **return** D3D\_SetError("CreateTexture()", result); 
58.  \} 
59. 
60. 
61.  result = 
62.  IDirect3DDevice9\_CreateTexture(renderdata->device, texture->w / 2, 
63.  texture->h / 2, 1, usage, 
64.  PixelFormatToD3DFMT(texture->format), 
65.  pool, &data->vtexture, NULL); 
66. **if** (FAILED(result)) \{ 
67. **return** D3D\_SetError("CreateTexture()", result); 
68.  \} 
69.  \} 
70. 
71. 
72. **return** 0; 
73. \}

从代码中可以看出，该函数调用了Direct3D的API函数IDirect3DDevice9\_CreateTexture()创建了一个纹理。

#### 2.OpenGL ####

OpenGL渲染器中对应CreateTexture()的函数是GL\_CreateTexture ()，它的源代码如下所示（位于render\\opengl\\SDL\_render\_gl.c）。

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1.  **static****int** GL\_CreateTexture(SDL\_Renderer \* renderer, SDL\_Texture \* texture) 
2.  \{ 
3.   GL\_RenderData \*renderdata = (GL\_RenderData \*) renderer->driverdata; 
4.   GL\_TextureData \*data; 
5.   GLint internalFormat; 
6.   GLenum format, type; 
7.  **int** texture\_w, texture\_h; 
8.   GLenum scaleMode; 
9.  
10. 
11.  GL\_ActivateRenderer(renderer); 
12. 
13. 
14. **if** (!convert\_format(renderdata, texture->format, &internalFormat, 
15.  &format, &type)) \{ 
16. **return** SDL\_SetError("Texture format %s not supported by OpenGL", 
17.  SDL\_GetPixelFormatName(texture->format)); 
18.  \} 
19. 
20. 
21.  data = (GL\_TextureData \*) SDL\_calloc(1, **sizeof**(\*data)); 
22. **if** (!data) \{ 
23. **return** SDL\_OutOfMemory(); 
24.  \} 
25. 
26. 
27. **if** (texture->access == SDL\_TEXTUREACCESS\_STREAMING) \{ 
28. **size\_t** size; 
29.  data->pitch = texture->w \* SDL\_BYTESPERPIXEL(texture->format); 
30.  size = texture->h \* data->pitch; 
31. **if** (texture->format == SDL\_PIXELFORMAT\_YV12 || 
32.  texture->format == SDL\_PIXELFORMAT\_IYUV) \{ 
33. /\* Need to add size for the U and V planes \*/
34.  size += (2 \* (texture->h \* data->pitch) / 4); 
35.  \} 
36.  data->pixels = SDL\_calloc(1, size); 
37. **if** (!data->pixels) \{ 
38.  SDL\_free(data); 
39. **return** SDL\_OutOfMemory(); 
40.  \} 
41.  \} 
42. 
43. 
44. **if** (texture->access == SDL\_TEXTUREACCESS\_TARGET) \{ 
45.  data->fbo = GL\_GetFBO(renderdata, texture->w, texture->h); 
46.  \} **else** \{ 
47.  data->fbo = NULL; 
48.  \} 
49. 
50. 
51.  GL\_CheckError("", renderer); 
52.  renderdata->glGenTextures(1, &data->texture); 
53. **if** (GL\_CheckError("glGenTexures()", renderer) < 0) \{ 
54.  SDL\_free(data); 
55. **return** \-1; 
56.  \} 
57.  texture->driverdata = data; 
58. 
59. 
60. **if** ((renderdata->GL\_ARB\_texture\_rectangle\_supported) 
61. /\* && texture->access != SDL\_TEXTUREACCESS\_TARGET \*/)\{ 
62.  data->type = GL\_TEXTURE\_RECTANGLE\_ARB; 
63.  texture\_w = texture->w; 
64.  texture\_h = texture->h; 
65.  data->texw = (GLfloat) texture\_w; 
66.  data->texh = (GLfloat) texture\_h; 
67.  \} **else** \{ 
68.  data->type = GL\_TEXTURE\_2D; 
69.  texture\_w = power\_of\_2(texture->w); 
70.  texture\_h = power\_of\_2(texture->h); 
71.  data->texw = (GLfloat) (texture->w) / texture\_w; 
72.  data->texh = (GLfloat) texture->h / texture\_h; 
73.  \} 
74. 
75. 
76.  data->format = format; 
77.  data->formattype = type; 
78.  scaleMode = GetScaleQuality(); 
79.  renderdata->glEnable(data->type); 
80.  renderdata->glBindTexture(data->type, data->texture); 
81.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MIN\_FILTER, scaleMode); 
82.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MAG\_FILTER, scaleMode); 
83. /\* According to the spec, CLAMP\_TO\_EDGE is the default for TEXTURE\_RECTANGLE
84.  and setting it causes an INVALID\_ENUM error in the latest NVidia drivers.
85.  \*/
86. **if** (data->type != GL\_TEXTURE\_RECTANGLE\_ARB) \{ 
87.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_S, 
88.  GL\_CLAMP\_TO\_EDGE); 
89.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_T, 
90.  GL\_CLAMP\_TO\_EDGE); 
91.  \} 
92. \#ifdef \_\_MACOSX\_\_
93. \#ifndef GL\_TEXTURE\_STORAGE\_HINT\_APPLE
94. \#define GL\_TEXTURE\_STORAGE\_HINT\_APPLE 0x85BC
95. \#endif
96. \#ifndef STORAGE\_CACHED\_APPLE
97. \#define STORAGE\_CACHED\_APPLE 0x85BE
98. \#endif
99. \#ifndef STORAGE\_SHARED\_APPLE
100. \#define STORAGE\_SHARED\_APPLE 0x85BF
101. \#endif
102. **if** (texture->access == SDL\_TEXTUREACCESS\_STREAMING) \{ 
103.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_STORAGE\_HINT\_APPLE, 
104.  GL\_STORAGE\_SHARED\_APPLE); 
105.  \} **else** \{ 
106.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_STORAGE\_HINT\_APPLE, 
107.  GL\_STORAGE\_CACHED\_APPLE); 
108.  \} 
109. **if** (texture->access == SDL\_TEXTUREACCESS\_STREAMING 
110.  && texture->format == SDL\_PIXELFORMAT\_ARGB8888 
111.  && (texture->w % 8) == 0) \{ 
112.  renderdata->glPixelStorei(GL\_UNPACK\_CLIENT\_STORAGE\_APPLE, GL\_TRUE); 
113.  renderdata->glPixelStorei(GL\_UNPACK\_ALIGNMENT, 1); 
114.  renderdata->glPixelStorei(GL\_UNPACK\_ROW\_LENGTH, 
115.  (data->pitch / SDL\_BYTESPERPIXEL(texture->format))); 
116.  renderdata->glTexImage2D(data->type, 0, internalFormat, texture\_w, 
117.  texture\_h, 0, format, type, data->pixels); 
118.  renderdata->glPixelStorei(GL\_UNPACK\_CLIENT\_STORAGE\_APPLE, GL\_FALSE); 
119.  \} 
120. **else**
121. \#endif
122.  \{ 
123.  renderdata->glTexImage2D(data->type, 0, internalFormat, texture\_w, 
124.  texture\_h, 0, format, type, NULL); 
125.  \} 
126.  renderdata->glDisable(data->type); 
127. **if** (GL\_CheckError("glTexImage2D()", renderer) < 0) \{ 
128. **return** \-1; 
129.  \} 
130. 
131. 
132. **if** (texture->format == SDL\_PIXELFORMAT\_YV12 || 
133.  texture->format == SDL\_PIXELFORMAT\_IYUV) \{ 
134.  data->yuv = SDL\_TRUE; 
135. 
136. 
137.  renderdata->glGenTextures(1, &data->utexture); 
138.  renderdata->glGenTextures(1, &data->vtexture); 
139.  renderdata->glEnable(data->type); 
140. 
141. 
142.  renderdata->glBindTexture(data->type, data->utexture); 
143.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MIN\_FILTER, 
144.  scaleMode); 
145.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MAG\_FILTER, 
146.  scaleMode); 
147.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_S, 
148.  GL\_CLAMP\_TO\_EDGE); 
149.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_T, 
150.  GL\_CLAMP\_TO\_EDGE); 
151.  renderdata->glTexImage2D(data->type, 0, internalFormat, texture\_w/2, 
152.  texture\_h/2, 0, format, type, NULL); 
153. 
154. 
155.  renderdata->glBindTexture(data->type, data->vtexture); 
156.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MIN\_FILTER, 
157.  scaleMode); 
158.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_MAG\_FILTER, 
159.  scaleMode); 
160.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_S, 
161.  GL\_CLAMP\_TO\_EDGE); 
162.  renderdata->glTexParameteri(data->type, GL\_TEXTURE\_WRAP\_T, 
163.  GL\_CLAMP\_TO\_EDGE); 
164.  renderdata->glTexImage2D(data->type, 0, internalFormat, texture\_w/2, 
165.  texture\_h/2, 0, format, type, NULL); 
166. 
167. 
168.  renderdata->glDisable(data->type); 
169.  \} 
170. 
171. 
172. **return** GL\_CheckError("", renderer); 
173. \}

从代码中可以看出，该函数调用了OpenGL的API函数glGenTextures()，glBindTexture()创建了一个纹理。并且使用glTexParameteri()设置了有关的一些参数。

在这里有一点需要注意，在OpenGL渲染器中，如果输入像素格式是YV12或者IYUV，就会使用3个纹理。

#### 3.Software ####

Software渲染器中对应CreateTexture()的函数是SW\_CreateTexture ()，它的源代码如下所示（位于render\\software\\SDL\_render\_sw.c）。

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1.  **static****int** SW\_CreateTexture(SDL\_Renderer \* renderer, SDL\_Texture \* texture) 
2.  \{ 
3.  **int** bpp; 
4.   Uint32 Rmask, Gmask, Bmask, Amask; 
5.  
6.  
7.  **if** (!SDL\_PixelFormatEnumToMasks 
8.   (texture->format, &bpp, &Rmask, &Gmask, &Bmask, &Amask)) \{ 
9.  **return** SDL\_SetError("Unknown texture format"); 
10.  \} 
11. 
12. 
13.  texture->driverdata = 
14.  SDL\_CreateRGBSurface(0, texture->w, texture->h, bpp, Rmask, Gmask, 
15.  Bmask, Amask); 
16.  SDL\_SetSurfaceColorMod(texture->driverdata, texture->r, texture->g, 
17.  texture->b); 
18.  SDL\_SetSurfaceAlphaMod(texture->driverdata, texture->a); 
19.  SDL\_SetSurfaceBlendMode(texture->driverdata, texture->blendMode); 
20. 
21. 
22. **if** (texture->access == SDL\_TEXTUREACCESS\_STATIC) \{ 
23.  SDL\_SetSurfaceRLE(texture->driverdata, 1); 
24.  \} 
25. 
26. 
27. **if** (!texture->driverdata) \{ 
28. **return** \-1; 
29.  \} 
30. **return** 0; 
31. \}

该函数的源代码还没有详细分析。可以看出其中调用了SDL\_CreateRGBSurface()创建了“Surface”。

[SDL2_1_SDL_Init]: http://blog.csdn.net/leixiaohua1020/article/details/40680907
[SDL2_2_SDL_Window]: http://blog.csdn.net/leixiaohua1020/article/details/40701203
[SDL2_3_SDL_Renderer]: http://blog.csdn.net/leixiaohua1020/article/details/40723085
[SDL2_4_SDL_Texture]: http://blog.csdn.net/leixiaohua1020/article/details/40743061
[SDL2_5_SDL_UpdateTexture]: http://blog.csdn.net/leixiaohua1020/article/details/40876089
[SDL2_6_SDL_RenderCopy]: http://blog.csdn.net/leixiaohua1020/article/details/40895593
[SDL2_7_SDL_RenderPresent]: http://blog.csdn.net/leixiaohua1020/article/details/40895797
[SDL2_8]: http://blog.csdn.net/leixiaohua1020/article/details/41207787
[20141103164709706]: /images/20220731/5635228fb10b49e7b777bac400cc645f.png
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