gelcounter/counter.c/counter.c

#include <math.h>
#include <stdio.h>
#include <cairo/cairo.h>
#include "counter.h"

static cairo_surface_t *digits[10];

void counter_init(void) {
  char buffer[16];

  for (int i = 0; i < 10; i++) {
    snprintf(buffer, sizeof(buffer), "./images/%d.png", i);

    digits[i] = cairo_image_surface_create_from_png(buffer);
  }
}

void counter_release(void) {
  for (int i = 0; i < 10; i++)
    cairo_surface_destroy(digits[i]);
}

static int count_digits(int number) {
  if (number < 10) return 1;
  if (number < 100) return 2;
  if (number < 1000) return 3;
  if (number < 10000) return 4;
  if (number < 100000) return 5;
  if (number < 1000000) return 6;
  if (number < 10000000) return 7;
  if (number < 100000000) return 8;
  if (number < 1000000000) return 9;

  return 10;
}

static int powersof10[] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000};

static int nth_digit(int number, int n) {
  return (number / powersof10[n]) % 10;
}

void counter_create(int number, char *filename) {
  int digits_count;
  cairo_surface_t *surface;
  cairo_t *cr;

  digits_count = count_digits(number);
  surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, digits_count * DIGIT_WIDTH, DIGIT_HEIGHT);
  cr = cairo_create(surface);
 
  for (int i = 0; i < digits_count; i++) {
    cairo_set_source_surface(cr, digits[nth_digit(number, digits_count-1-i)], i * DIGIT_WIDTH, 0);
    cairo_paint(cr);
  }

  cairo_surface_write_to_png(surface, filename);
  cairo_surface_destroy(surface);
  cairo_destroy(cr);
}