draw_trans_sprite(3)

✨ draw_trans_sprite ✨

okay bestie, gather round, because today we're talking about draw_trans_sprite from the Allegro manual 💅 this is a function that draws a sprite and blends it with the destination — it's from the Allegro game programming library, and it's lowkey iconic for ghost effects 🫶

🌸 SYNOPSIS 🌸

#include <allegro.h>

void draw_trans_sprite(BITMAP *bmp, BITMAP *sprite, int x, int y);

🦋 DESCRIPTION 🦋

so what it does is: it uses the global color_map table, or the truecolor blender functions, to overlay the sprite on top of the existing image ✨

⚠️ important bestie: this must only be used after you've set up the color mapping table (for 256-color modes) or the blender functions (for truecolor modes). no setup, no slay. 😭

and because translucent drawing involves reading as well as writing the bitmap memory, it is very slow if you draw directly to video RAM 💀 so wherever possible you should use a memory bitmap instead. fr fr, take the hint.

example time, look at her go:

/* Some one time initialisation code. */
COLOR_MAP global_trans_table;
create_trans_table(&global_trans_table, my_palette,
                   128, 128, 128, NULL);
...
if (get_color_depth() == 8)
   color_map = &global_trans_table;
else
   set_trans_blender(128, 128, 128, 128);

draw_trans_sprite(buffer, ghost_sprite, x, y);

now, the tea about color depths 🍓 — the bitmap and the sprite must normally be in the same color depth. but as a special case:

• you can draw 32 bit RGBA format sprites onto any hicolor or truecolor bitmap, as long as you call set_alpha_blender() first 👑
• and you can draw 8-bit alpha images onto a 32-bit RGBA destination, as long as you call set_write_alpha_blender() first 💖

and just like draw_sprite(), this function skips transparent pixels — except if the source sprite is an 8-bit image. if that's the case, bestie, you should pay attention to properly setting up your color map table for index 0 🙈 don't skip that part, it matters.

🌈 SEE ALSO 🌈

• draw_sprite(3)
• draw_lit_sprite(3)
• draw_trans_rle_sprite(3)
• color_map(3)
• set_trans_blender(3)
• set_alpha_blender(3)
• set_write_alpha_blender(3)
• bitmap_mask_color(3)
• exalpha(3)
• exblend(3)
• exlights(3)
• exrotscl(3)
• extrans(3)
• exxfade(3)

and that's the whole vibe check, bestie 🎀 this was draw_trans_sprite(3) from the Allegro manual, version 4.4.3 — go forth and blend your sprites, you absolute main character 💜✨