blit(3alleg4)

💖 blit — the Allegro manual, but make it slay 💖

okay bestie, welcome to blit(3alleg4) — straight out of the Allegro manual, and she's a legend. This one copies a rectangular area from one bitmap to another. Allegro game programming library energy, fr fr. 🎀

✨ SYNOPSIS ✨

#include <allegro.h>

void blit(BITMAP *source, BITMAP *dest, int source_x, int source_y, int
dest_x, int dest_y, int width, int height);

🌸 DESCRIPTION 🌸

So basically, blit copies a rectangular area of the source bitmap over to the destination bitmap. The source_x and source_y parameters are the top left corner of the area you're copying from the source, and dest_x and dest_y are the matching position over in the destination. 💅

She respects the destination clipping rectangle, no cap — and she'll also clip if you try to blit from areas outside the source bitmap. Iconic behavior, honestly.

Example time, bestie:

BITMAP *bmp;
...
/* Blit src on the screen. */
blit(bmp, screen, 0, 0, 0, 0, bmp->w, bmp->h);

/* Now copy a chunk to a corner, slightly outside. /*
blit(screen, screen, 100, 100, -10, -10, 25, 30);

You can blit between any parts of any two bitmaps, even if the two memory areas overlap (ie. source and dest are the same, or one is a sub-bitmap of the other). But bestie, hear me out — a lot of SVGA cards don't provide separate read and write banks, which means blitting from one part of the screen to another requires a temporary bitmap in memory, and is therefore extremely slow. 😭 As a general rule, avoid blitting from the screen onto itself in SVGA modes. That's the vibe check.

In mode-X, though? Whole different story. Blitting from one part of the screen to another can be significantly faster than blitting from memory onto the screen — as long as the source and destination are correctly aligned with each other. Copying between overlapping screen rectangles is slow, but if the areas don't overlap, and if they have the same plane alignment (ie. (source_x%4) == (dest_x%4)), the VGA latch registers can be used for a very fast data transfer. 🔥 To take advantage of this, in mode-X it is often worth storing tile graphics in a hidden area of video memory (using a large virtual screen), and blitting them from there onto the visible part of the screen. main character move, honestly.

If the GFX_HW_VRAM_BLIT bit in the gfx_capabilities flag is set, the current driver supports hardware accelerated blits from one part of the screen onto another. This is extremely fast, so when this flag is set it may be worth storing some of your more frequently used graphics in an offscreen portion of the video memory. obsessed. 👑

Unlike most of the graphics routines, blit() allows the source and destination bitmaps to be of different color depths, so it can be used to convert images from one pixel format to another. In this case, the behavior is affected by the COLORCONV_KEEP_TRANS and COLORCONV_DITHER* flags of the current color conversion mode: see set_color_conversion() for more information. 🦋

💜 SEE ALSO 💜

• masked_blit(3alleg4)
• stretch_blit(3alleg4)
• draw_sprite(3alleg4)
• gfx_capabilities(3alleg4)
• set_color_conversion(3alleg4)

go read those too bestie, iykyk 🫶

and that's the whole page, periodt. 💖 this was Allegro, version 4.4.3, and the page is blit(3alleg4) — stay slay, go blit something pretty ✨🌸💅