1set_write_alpha_blender(3) Allegro manual set_write_alpha_blender(3)
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6 set_write_alpha_blender - Enables the special alpha-channel editing
7 mode. Allegro game programming library.
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10 #include <allegro.h>
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13 void set_write_alpha_blender();
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16 Enables the special alpha-channel editing mode, which is used for draw‐
17 ing alpha channels over the top of an existing 32-bit RGB sprite, to
18 turn it into an RGBA format image. After calling this function, you can
19 set the drawing mode to DRAW_MODE_TRANS and then write draw color val‐
20 ues (0-255) onto a 32-bit image. This will leave the color values
21 unchanged, but alter the alpha to whatever values you are writing.
22 After enabling this mode you can also use draw_trans_sprite() to super‐
23 impose an 8-bit alpha mask over the top of an existing 32-bit sprite.
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27 set_alpha_blender(3), draw_trans_sprite(3), drawing_mode(3), exal‐
28 pha(3), extrans(3)
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32Allegro version 4.2.3 set_write_alpha_blender(3)