Function truncate_bitmap_buffer

src/lib/vga_gfx.c:158–245

* Truncates the content of the bitmap buffer in-place, moving * set pixels to the top-left corner and clearing the rest. * Ensures truncated width and height are multiples of 8. * @param truncated_width Output pointer for the new width. * @param truncated_height Output pointer for the new height. */

 * @param truncated_height Output pointer for the new height.
 */
static void truncate_bitmap_buffer(
	int *truncated_width, int *truncated_height)
{
	int min_pixel_x = INT_MAX, max_pixel_x = INT_MIN;
	int min_pixel_y = INT_MAX, max_pixel_y = INT_MIN;
	bool found_pixel = false;

	/* Validate input params */
	if (!truncated_width || !truncated_height)
		return;

	/* Scan the source buffer to find the actual bounding box of
	 * set pixels
	 */
	for (int y = 0; y < buffer_height; y++) {
		for (int x = 0; x < buffer_width; x++) {
			if (get_raw_pixel(x, y)) {
				min_pixel_x = MIN(min_pixel_x, x);
				max_pixel_x = MAX(max_pixel_x, x);
				min_pixel_y = MIN(min_pixel_y, y);
				max_pixel_y = MAX(max_pixel_y, y);
				found_pixel = true;
			}
		}
	}

	if (!found_pixel) {
		/* No set pixels found, effectively empty. */
		memset(buffer, 0, buffer_width * buffer_height / BITS_PER_BYTE);
		*truncated_width = 0;
		*truncated_height = 0;
		printk(BIOS_ERR, "BITMAP: Unable to crop. No pixels\n");
		return;
	}

	/*
	 * The width of the truncated content in pixels, rounded up to
	 * multiple of FONT_WIDTH.
	 */
	int min_byte_x = (min_pixel_x / BITS_PER_BYTE);
	int max_byte_x = (max_pixel_x / BITS_PER_BYTE);
	int new_content_width = (max_byte_x - min_byte_x + 1) * BITS_PER_BYTE;
	new_content_width += FONT_WIDTH - 1;
	new_content_width /= FONT_WIDTH;
	new_content_width *= FONT_WIDTH;
	new_content_width = MIN(new_content_width, buffer_width);

	/*
	 * The height of the truncated content in pixels, rounded up to
	 * multiple of FONT_HEIGHT.
	 */
	int new_content_height = max_pixel_y - min_pixel_y + 1;
	new_content_height += FONT_HEIGHT - 1;
	new_content_height /= FONT_HEIGHT;
	new_content_height *= FONT_HEIGHT;
	new_content_height = MIN(new_content_height, buffer_height);

	/* Calculate number of bytes per row */