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This thread is locked; no one can reply to it.
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| [A5] how to use a bitmap as a pattern to fill a rectangular area? |
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axilmar
Member #1,204
April 2001
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Hi, I'd like to fill a rectangular area with a bitmap used as a pattern. How do I do that with A5? |
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Don Freeman
Member #5,110
October 2004
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Use the primitives addon. Look at the source code for the primitives example... -- |
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axilmar
Member #1,204
April 2001
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Thanks. After lots of experimentation, I came up with this: 1void al_draw_bitmap_rect(ALLEGRO_BITMAP *bmp, int sx, int sy, int sw, int sh, float dx, float dy, float dw, float dh, int flags) {
2 ALLEGRO_BITMAP *sub = al_create_sub_bitmap(bmp, sx, sy, sw, sh);
3 ALLEGRO_BITMAP *clone = al_clone_bitmap(sub);
4
5 ALLEGRO_COLOR c = al_map_rgb(255, 255, 255);
6
7 ALLEGRO_VERTEX vertices[4];
8
9 vertices[0].x = dx;
10 vertices[0].y = dy;
11 vertices[0].z = 0;
12 vertices[0].color = c;
13 vertices[0].u = 0;
14 vertices[0].v = 0;
15
16 vertices[1].x = dx + dw;
17 vertices[1].y = dy;
18 vertices[1].z = 0;
19 vertices[1].color = c;
20 vertices[1].u = dw;
21 vertices[1].v = 0;
22
23 vertices[2].x = dx;
24 vertices[2].y = dy + dh;
25 vertices[2].z = 0;
26 vertices[2].color = c;
27 vertices[2].u = 0;
28 vertices[2].v = dh;
29
30 vertices[3].x = dx + dw;
31 vertices[3].y = dy + dh;
32 vertices[3].z = 0;
33 vertices[3].color = c;
34 vertices[3].u = dw;
35 vertices[3].v = dh;
36
37 al_draw_prim(vertices, nullptr, clone, 0, 4, ALLEGRO_PRIM_TRIANGLE_STRIP);
38
39 al_destroy_bitmap(clone);
40 al_destroy_bitmap(sub);
41}
Am I doing it correctly? the visual output seems correct. The function obviously creates and destroys bitmaps, so it's not the fastest thing. Other than pre-creating the bitmaps, is there another way to specify a subarea of the bitmap? perhaps using the vertices? |
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SiegeLord
Member #7,827
October 2006
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axilmar said: Other than pre-creating the bitmaps, is there another way to specify a subarea of the bitmap? perhaps using the vertices? Can't be done without shaders, which is why Allegro doesn't support this operation. "For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18 |
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axilmar
Member #1,204
April 2001
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SiegeLord said: Can't be done without shaders, which is why Allegro doesn't support this operation. Thanks. So it seems I would have to actually split the bitmap into other bitmaps. |
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