tex_bmp.cpp

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/* Copyright (c) 2010 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Windows BMP codec
 */

#include "precompiled.h"

#include "lib/byte_order.h"
#include "tex_codec.h"

#pragma pack(push, 1)

struct BmpHeader
{ 
    // BITMAPFILEHEADER
    u16 bfType;         // "BM"
    u32 bfSize;         // of file
    u16 bfReserved1;
    u16 bfReserved2;
    u32 bfOffBits;      // offset to image data

    // BITMAPINFOHEADER
    u32 biSize;
    i32 biWidth;
    i32 biHeight;
    u16 biPlanes;
    u16 biBitCount;
    u32 biCompression;
    u32 biSizeImage;
    // the following are unused and zeroed when writing:
    i32 biXPelsPerMeter;
    i32 biYPelsPerMeter;
    u32 biClrUsed;
    u32 biClrImportant;
};

#pragma pack(pop)

#define BI_RGB 0        // biCompression


static Status bmp_transform(Tex* UNUSED(t), size_t UNUSED(transforms))
{
    return INFO::TEX_CODEC_CANNOT_HANDLE;
}


static bool bmp_is_hdr(const u8* file)
{
    // check header signature (bfType == "BM"?).
    // we compare single bytes to be endian-safe.
    return (file[0] == 'B' && file[1] == 'M');
}


static bool bmp_is_ext(const OsPath& extension)
{
    return extension == L".bmp";
}


static size_t bmp_hdr_size(const u8* file)
{
    const size_t hdr_size = sizeof(BmpHeader);
    if(file)
    {
        BmpHeader* hdr = (BmpHeader*)file;
        const u32 ofs = read_le32(&hdr->bfOffBits);
        ENSURE(ofs >= hdr_size && "bmp_hdr_size invalid");
        return ofs;
    }
    return hdr_size;
}


// requirements: uncompressed, direct colour, bottom up
static Status bmp_decode(rpU8 data, size_t UNUSED(size), Tex* RESTRICT t)
{
    const BmpHeader* hdr = (const BmpHeader*)data;
    const long w       = (long)read_le32(&hdr->biWidth);
    const long h_      = (long)read_le32(&hdr->biHeight);
    const u16 bpp      = read_le16(&hdr->biBitCount);
    const u32 compress = read_le32(&hdr->biCompression);

    const long h = abs(h_);

    size_t flags = 0;
    flags |= (h_ < 0)? TEX_TOP_DOWN : TEX_BOTTOM_UP;
    if(bpp > 16)
        flags |= TEX_BGR;
    if(bpp == 32)
        flags |= TEX_ALPHA;

    // sanity checks
    if(compress != BI_RGB)
        WARN_RETURN(ERR::TEX_COMPRESSED);

    t->w     = w;
    t->h     = h;
    t->bpp   = bpp;
    t->flags = flags;
    return INFO::OK;
}


static Status bmp_encode(Tex* RESTRICT t, DynArray* RESTRICT da)
{
    const size_t hdr_size = sizeof(BmpHeader);  // needed for BITMAPFILEHEADER
    const size_t img_size = tex_img_size(t);
    const size_t file_size = hdr_size + img_size;
    const i32 h = (t->flags & TEX_TOP_DOWN)? -(i32)t->h : (i32)t->h;

    size_t transforms = t->flags;
    transforms &= ~TEX_ORIENTATION; // no flip needed - we can set top-down bit.
    transforms ^= TEX_BGR;          // BMP is native BGR.

    const BmpHeader hdr =
    {
        // BITMAPFILEHEADER
        0x4D42,             // bfType = 'B','M'
        (u32)file_size,     // bfSize
        0, 0,               // bfReserved1,2
        hdr_size,           // bfOffBits

        // BITMAPINFOHEADER
        40,                 // biSize = sizeof(BITMAPINFOHEADER)
        (i32)t->w,
        h,
        1,                  // biPlanes
        (u16)t->bpp,
        BI_RGB,             // biCompression
        (u32)img_size,      // biSizeImage
        0, 0, 0, 0          // unused (bi?PelsPerMeter, biClr*)
    };
    return tex_codec_write(t, transforms, &hdr, hdr_size, da);
}

TEX_CODEC_REGISTER(bmp);