gp_bmp.h

// SPDX-License-Identifier: LGPL-2.1-or-later
/*
 * Copyright (C) 2009-2020 Cyril Hrubis <metan@ucw.cz>
 */
 
/*
 
   Internal BMP loader functions, you shouldn't need to touch these unless you
   need to parse file formats that embedds a BMP images with incomplete header
   such as ICO file format.
 
 */
 
#ifndef GP_BMP_H
#define GP_BMP_H
 
/*
 * Sometimes called a DIB header as well.
 */
struct gp_bmp_info_header {
        /* Offset to image data */
        uint32_t pixel_offset;
 
        /* Offset to the start of the info header */
        uint32_t header_offset;
 
        /* Header size (palette is on offset header_size + 14) */
        uint32_t header_size;
 
        /*
         * Image size in pixels.
         *
         * If h is negative image is top-down (bottom-up is default)
         */
        int32_t w;
        int32_t h;
 
        uint16_t bpp;
        uint32_t compress_type;
        /*
         * if 0 image uses whole range (2^bpp colors)
         */
        uint32_t palette_colors;
        /*
         * RGBA masks for bitfields compression
         */
        uint32_t R_mask;
        uint32_t G_mask;
        uint32_t B_mask;
        uint32_t A_mask;
};
 
enum gp_bmp_compress {
        COMPRESS_RGB            = 0, /* uncompressed */
        COMPRESS_RLE8           = 1, /* run-length encoded bitmap */
        COMPRESS_RLE4           = 2, /* run-length encoded bitmap */
        COMPRESS_BITFIELDS      = 3, /* bitfield for each channel */
        COMPRESS_JPEG           = 4, /* only for printers */
        COMPRESS_PNG            = 5, /* only for printers */
        COMPRESS_ALPHABITFIELDS = 6,
        COMPRESS_MAX = COMPRESS_ALPHABITFIELDS,
};
 
enum gp_bmp_info_header_size {
        BITMAPCOREHEADER  = 12,  /* old OS/2 format + win 3.0             */
        BITMAPCOREHEADER2 = 64,  /* OS/2                                  */
        BITMAPINFOHEADER  = 40,  /* most common                           */
        BITMAPINFOHEADER2 = 52,  /* Undocummented                         */
        BITMAPINFOHEADER3 = 56,  /* Undocummented                         */
        BITMAPINFOHEADER4 = 108, /* adds color space + gamma - win 95/NT4 */
        BITMAPINFOHEADER5 = 124, /* adds ICC color profiles win 98+       */
};
 
/*
 * @brief Attempts to parse BMP info header at current offset in the file IO.
 *
 * Note that pixel_offset is not set by this function since the offset to the
 * pixels is stored in the bitmap file header. This offset must be filled in by
 * the called before the header is passed to gp_bmp_read_pixels() function.
 *
 * @io     An io stream with an BMP info header at current offset.
 * @header BMP info header to be filled in.
 *
 * @return Returns 0 on success and errno on a failure.
 */
int gp_bmp_read_info_header(gp_io *io, struct gp_bmp_info_header *header);
 
/*
 * @brief Returns a pixel type suitable for a BMP info header.
 *
 * Returns a pixel type suitable for an pixmap that could be later passed to
 * the gp_bmp_read_pixels().
 *
 * @header BMP info header.
 *
 * @return A pixel type.
 */
gp_pixel_type gp_bmp_pixel_type(struct gp_bmp_info_header *header);
 
/*
 * @brief Returns palette size in bytes.
 *
 * @header BMP info header structure.
 *
 * @return Palette size in bytes.
 */
uint32_t gp_bmp_palette_size(struct gp_bmp_info_header *header);
 
/*
 * @brief Reads a pixel data.
 *
 * @io An io stream.
 * @header BMP info header.
 * @pixmap Pre-allocated pixmap of correct size and pixel type.
 * @callback A progress callback.
 *
 * @return Returns 0 on success and errno on a failure.
 */
int gp_bmp_read_pixels(gp_io *io, struct gp_bmp_info_header *header,
                       gp_pixmap *pixmap, gp_progress_cb *callback);
 
#endif /* GP_BMP_H */