Optimization of ImageDrawRectangleRec()

[smalltimewizard]

A significant performance increase can be had by copying the first row to all other rows.

[raysan5]

@smalltimewizard did you review the performance gain? Please, could you provide more info, and example or some metrics?

[smalltimewizard]

The following code performs a barebones test.

// gcc main.c -o bench.exe -I "./include" -L "./lib" -lraylib -lgdi32 -lwinmm

#include <stdio.h>
#include <time.h>

#include "raylib.h"

#define GRIDW 64
#define GRIDH 64
#define CELLW 24
#define CELLH 24
#define RUNS 10000

int main(int argc, char* argv[]) {
	SetTraceLogLevel(LOG_WARNING);
	
	Image benchimage = {0};
	benchimage = GenImageColor(GRIDW * CELLW, GRIDH * CELLH, (Color){0,0,0,0}); // Set transparent image of the proper size
	ImageFormat(&benchimage, PIXELFORMAT_UNCOMPRESSED_R8G8B8A8);
	
	double timerstart = (double) clock();
	
	int runs = 0;
	while (runs < RUNS) {
		for (int i = 0; i < GRIDW * GRIDH; i++) {
			ImageDrawRectangleRec(&benchimage, (Rectangle){(i % GRIDW) * CELLW, (i / GRIDW) * CELLH, CELLW, CELLH}, (Color){GetRandomValue(0,255), GetRandomValue(0,255), GetRandomValue(0,255), 255});
		}
		runs++;
	}
	
	printf("%d calls took %f seconds to run.", GRIDW * GRIDH * RUNS, (double) (clock() - timerstart)/CLOCKS_PER_SEC);
	
	return 0;
};

This is 40,960,000 calls, fully replacing a 64x64 grid of 24x24 randomly-colored squares 10,000 times.
Without the change (libraylib.a from raylib-4.5.0_win64_mingw-w64), it takes ~105 seconds to run on my machine.
With the change (libraylib.a compiled with mingw32-make), it takes ~19 seconds.

[smalltimewizard]

The program where I was trying to use this before/after (55 FPS vs 128 FPS):


85x64 grid refreshed each frame with randomly-colored 24x24 squares. And a bit of other stuff that shouldn't affect the overhead much.

[raysan5]

@smalltimewizard thank you very much for the benchmark, reviewed and verified that the improvement is considerable, it went from 160 seconds to 14 seconds on my system (11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz, Windows 10 Pro 64bit, compiled with GCC 12.2.0).