SDL_UpdateTexture、SDL_RenderCopy、SDL_RenderReadPixels的花费时间

ancientcc

1. surface render_scale_surface(const surface &surf, int w, int h)
   
2. {
   
3.         tblend_none_lock lock(surf);
   
4. 
   
5.         uint32_t t1, t2, t3, t4, t5;
   
6.         t1 = SDL_GetTicks();
   
7. 
   
8.         SDL_Texture* src = SDL_CreateTextureFromSurface(renderer, surf);
   
9.         SDL_Texture* target = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, w, h);
   
10.         SDL_SetRenderTarget(renderer, target);
    
11. 
    
12.         t2 = SDL_GetTicks();
    
13.         SDL_RenderCopy(renderer, src, NULL, NULL);
    
14.         t3 = SDL_GetTicks();
    
15. 
    
16.         surface dst(create_neutral_surface(w, h));
    
17.         {
    
18.                 surface_lock dst_lock(dst);
    
19.                 t4 = SDL_GetTicks();
    
20.                 SDL_RenderReadPixels(renderer, NULL, SDL_PIXELFORMAT_ARGB8888, dst->pixels, 4 * w);
    
21.         }
    
22.         t5 = SDL_GetTicks();
    
23.         posix_print("create: %i, RenderCopy: %i, create2: %i, ReadPixels: %i\n", t2 - t1, t3 - t2, t4 - t3, t5 - t4);
    
24. 
    
25.         SDL_SetRenderTarget(renderer, NULL);
    
26.         SDL_DestroyTexture(target);
    
27.         SDL_DestroyTexture(src);
    
28.         return dst;
    
29. }

复制代码

上面是一个执行缩功能的函数，它同时用到了这三个函数，并打印它们花费的时间。打印部分见后面。

1. create: 31, RenderCopy: 4, create2: 6, ReadPixels: 16
   
2. (750x1334)==>(640x1136), soft: 65, gpu: 61

复制代码

以以上这条记录为例说明各字段。它们时间单位都是毫秒

字段
create	会调用SDL_CreateTexture，该函数要执行SDL_UpdateTexture，它花费的时间基本花费在SDL_UpdateTexture
RenderCopy	花费在SDL_RenderCopy的时间
create2	创建目标图面，和opengl无关
ReadPixels	花费在SDL_RenderReadPixels上时间
(750x1334)==>(640x1136)	指示这次缩放的(源图像尺寸)==>(目标图像尺寸)
soft	缩放这个图像，scale_surface花费了的时间。相比opengl使用GPU，把它称为软缩放
gpu	缩放这个图像，render_scale_surface花费了的时间，就是以上那几个时间之和

根据察看打印得出的几个结论。

• 执行SDL_UpdateTexture，Android要比iOS快。不过iOS慢也不算离谱，还能接受。
• 执行SDL_RenderCopy，不论Android还是iOS，都快。
• 执行SDL_RenderReadPixels，都不算快，尤其Android，只能用慢到离谱来形容。
• 对缩放小图像，像<100x100的，因为GPU有固定消耗在那里，相比软缩放没优势，但图像越大，它的优势越明显。
• 程序应该尽量避免SDL_RenderReadPixels！
  

iOS
create: 31, RenderCopy: 4, create2: 6, ReadPixels: 16
(750x1334)==>(640x1136), soft: 65, gup: 61
create: 35, RenderCopy: 0, create2: 6, ReadPixels: 17
(750x1334)==>(640x1136), soft: 394, gup: 62
create: 4, RenderCopy: 0, create2: 1, ReadPixels: 2
(224x224)==>(220x220), soft: 6, gup: 8
create: 5, RenderCopy: 0, create2: 6, ReadPixels: 17
(750x133)==>(640x1136), soft: 45, gup: 30
2create: 2, RenderCopy: 0, create2: 5, ReadPixels: 15
(100x100)==>(640x1008), soft: 38, gup: 23
create: 2, RenderCopy: 0, create2: 1, ReadPixels: 2
(224x224)==>(220x220), soft: 6, gup: 6
create: 5, RenderCopy: 0, create2: 6, ReadPixels: 17
(750x133)==>(640x1136), soft: 43, gup: 30
create: 31, RenderCopy: 0, create2: 4, ReadPixels: 16
(750x1131)==>(640x780), soft: 234, gup: 54
create: 5, RenderCopy: 0, create2: 1, ReadPixels: 4
(266x600)==>(266x346), soft: 13, gup: 11
create: 1, RenderCopy: 1, create2: 1, ReadPixels: 5
(100x100)==>(640x244), soft: 9, gup: 9
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 1
(24x24)==>(48x48), soft: 1, gup: 3
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 2
(80x80)==>(76x76), soft: 1, gup: 4
create: 37, RenderCopy: 1, create2: 6, ReadPixels: 29
(750x1334)==>(640x1136), soft: 143, gup: 77
create: 1, RenderCopy: 1, create2: 0, ReadPixels: 1
(126x1)==>(368x1), soft: 0, gup: 3
create: 0, RenderCopy: 0, create2: 0, ReadPixels: 2
(24x24)==>(48x48), soft: 1, gup: 2
create: 0, RenderCopy: 0, create2: 1, ReadPixels: 1
(126x1)==>(368x1), soft: 0, gup: 2
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 1
(24x24)==>(48x48), soft: 0, gup: 3
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 2
(126x1)==>(368x1), soft: 0, gup: 3
create: 0, RenderCopy: 1, create2: 0, ReadPixels: 1
(24x24)==>(48x48), soft: 1, gup: 2
create: 20, RenderCopy: 0, create2: 4, ReadPixels: 14
(640x1136)==>(531x944), soft: 217, gup: 41
create: 33, RenderCopy: 0, create2: 6, ReadPixels: 38
(750x1334)==>(640x1136), soft: 143, gup: 82
create: 28, RenderCopy: 0, create2: 6, ReadPixels: 17
(750x1334)==>(640x1136), soft: 144, gup: 55


Android
create: 15, RenderCopy: 3, create2: 14, ReadPixels: 189
(750x1334)==>(1080x1860), soft: 73, gup: 224
create: 19, RenderCopy: 0, create2: 22, ReadPixels: 212
(750x1334)==>(1080x1860), soft: 286, gup: 257
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 3
(88x88)==>(132x132), soft: 1, gup: 4
create: 0, RenderCopy: 1, create2: 0, ReadPixels: 12
(224x224)==>(336x336), soft: 7, gup: 13
create: 1, RenderCopy: 0, create2: 1, ReadPixels: 10
(224x224)==>(336x336), soft: 6, gup: 13
create: 1, RenderCopy: 0, create2: 1, ReadPixels: 7
(88x88)==>(126x126), soft: 2, gup: 9
create: 0, RenderCopy: 0, create2: 1, ReadPixels: 2
(88x88)==>(132x132), soft: 2, gup: 3
create: 17, RenderCopy: 0, create2: 29, ReadPixels: 169
(750x1334)==>(1080x1860), soft: 133, gup: 218
create: 0, RenderCopy: 0, create2: 0, ReadPixels: 2
(126x1)==>(648x1), soft: 0, gup: 2
create: 0, RenderCopy: 0, create2: 0, ReadPixels: 1
(24x24)==>(72x72), soft: 1, gup: 1
create: 0, RenderCopy: 0, create2: 0, ReadPixels: 0
(126x1)==>(648x1), soft: 0, gup: 0
create: 0, RenderCopy: 0, create2: 0, ReadPixels: 9
(24x24)==>(72x72), soft: 0, gup: 9
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 1
(126x1)==>(648x1), soft: 1, gup: 2
create: 1, RenderCopy: 0, create2: 0, ReadPixels: 1
(24x24)==>(72x72), soft: 0, gup: 2
create: 32, RenderCopy: 0, create2: 8, ReadPixels: 200
(1080x1860)==>(912x1572), soft: 199, gup: 243
create: 16, RenderCopy: 0, create2: 14, ReadPixels: 160
(750x1334)==>(1080x1860), soft: 140, gup: 194
create: 0, RenderCopy: 0, create2: 1, ReadPixels: 2
(88x88)==>(132x132), soft: 2, gup: 3
create: 1, RenderCopy: 1, create2: 0, ReadPixels: 21
(224x224)==>(336x336), soft: 7, gup: 23
create: 1, RenderCopy: 0, create2: 1, ReadPixels: 24
(224x224)==>(336x336), soft: 14, gup: 26