background.c File Reference

Scalar ASCII background color rendering (truecolor) More...

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Functions
char *	image_print_color_background (const image_t *p, const char *palette)
	Convert image to colored ASCII art with background colors.

Detailed Description

Scalar ASCII background color rendering (truecolor)

Renders images using ANSI truecolor background colors with contrasting foreground text. Background is set to the pixel color, foreground is white on dark pixels, black on bright pixels.

Definition in file background.c.

Function Documentation

image_print_color_background()

char * image_print_color_background	(	const image_t *	p,
		const char *	palette
	)

Convert image to colored ASCII art with background colors.

Parameters

p	Image pointer
palette	Character palette for luminance mapping

Returns

Allocated ASCII string with background color codes (caller must free), or NULL on error

Definition at line 17 of file background.c.

                                                                          {
  if (!p || !palette || !p->pixels) {
    return NULL;
  }
 
  utf8_palette_cache_t *utf8_cache = get_utf8_palette_cache(palette);
  if (!utf8_cache) {
    return NULL;
  }
 
  const int h = p->h;
  const int w = p->w;
  const size_t h_sz = (size_t)h;
  const size_t w_sz = (size_t)w;
 
  if (h_sz > 0 && w_sz > SIZE_MAX / h_sz) {
    return NULL;
  }
 
  // Each pixel needs: bg sequence (~19) + fg sequence (~19) + char (up to 4) + possible reset
  const size_t bytes_per_pixel = 50;
  const size_t total_pixels = h_sz * w_sz;
  const size_t lines_size = total_pixels * bytes_per_pixel + h_sz + 16;
 
  char *lines;
  lines = SAFE_MALLOC(lines_size, char *);
 
  char *ptr = lines;
  const rgb_pixel_t *pix = p->pixels;
 
  for (int y = 0; y < h; y++) {
    const int row_offset = y * w;
 
    for (int x = 0; x < w; x++) {
      const rgb_pixel_t pixel = pix[row_offset + x];
 
      // Set background to pixel color
      ptr += SAFE_SNPRINTF(ptr, 20, "\033[48;2;%d;%d;%dm", pixel.r, pixel.g, pixel.b);
 
      // Choose contrasting foreground: white on dark, black on bright
      int luminance = (77 * pixel.r + 150 * pixel.g + 29 * pixel.b + 128) >> 8;
      if (luminance < 128) {
        ptr += SAFE_SNPRINTF(ptr, 20, "\033[38;2;255;255;255m");
      } else {
        ptr += SAFE_SNPRINTF(ptr, 20, "\033[38;2;0;0;0m");
      }
 
      // Select character based on luminance
      uint8_t safe_luminance = clamp_rgb(luminance);
      const utf8_char_t *char_info = &utf8_cache->cache[safe_luminance];
      for (int i = 0; i < char_info->byte_len; i++) {
        *ptr++ = char_info->utf8_bytes[i];
      }
    }
 
    // Reset and newline
    *ptr++ = '\033';
    *ptr++ = '[';
    *ptr++ = '0';
    *ptr++ = 'm';
    if (y < h - 1) {
      *ptr++ = '\n';
    }
  }
 
  *ptr = '\0';
  return lines;
}

References rgb_pixel_t::b, utf8_char_t::byte_len, utf8_palette_cache::cache, rgb_pixel_t::g, get_utf8_palette_cache(), image_t::h, image_t::pixels, rgb_pixel_t::r, SAFE_MALLOC, SAFE_SNPRINTF, utf8_char_t::utf8_bytes, and image_t::w.

Referenced by ascii_convert(), and image_print_with_capabilities().