tex_tga.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.
 */

/*
 * TGA codec.
 */

#include "precompiled.h"

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

#pragma pack(push, 1)

enum TgaImgType
{
    TGA_TRUE_COLOUR = 2,    // uncompressed 24 or 32 bit direct RGB
    TGA_GREY        = 3     // uncompressed 8 bit direct greyscale
};

enum TgaImgDesc
{
    TGA_RIGHT_TO_LEFT = BIT(4),
    TGA_TOP_DOWN      = BIT(5),
};

typedef struct
{
    u8 img_id_len;          // 0 - no image identifier present
    u8 colour_map_type;     // 0 - no colour map present
    u8 img_type;            // see TgaImgType
    u8 colour_map[5];       // unused

    u16 x_origin;           // unused
    u16 y_origin;           // unused

    u16 w;
    u16 h;
    u8 bpp;                 // bits per pixel

    u8 img_desc;
}
TgaHeader;

// TGA file: header [img id] [colour map] image data

#pragma pack(pop)


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


static bool tga_is_hdr(const u8* file)
{
    TgaHeader* hdr = (TgaHeader*)file;

    // the first TGA header doesn't have a magic field;
    // we can only check if the first 4 bytes are valid
    // .. not direct colour
    if(hdr->colour_map_type != 0)
        return false;
    // .. wrong colour type (not uncompressed greyscale or RGB)
    if(hdr->img_type != TGA_TRUE_COLOUR && hdr->img_type != TGA_GREY)
        return false;

    // note: we can't check img_id_len or colour_map[0] - they are
    // undefined and may assume any value.

    return true;
}


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


static size_t tga_hdr_size(const u8* file)
{
    size_t hdr_size = sizeof(TgaHeader);
    if(file)
    {
        TgaHeader* hdr = (TgaHeader*)file;
        hdr_size += hdr->img_id_len;
    }
    return hdr_size;
}


// requirements: uncompressed, direct color, bottom up
static Status tga_decode(rpU8 data, size_t UNUSED(size), Tex* RESTRICT t)
{
    const TgaHeader* hdr = (const TgaHeader*)data;
    const u8 type  = hdr->img_type;
    const size_t w   = read_le16(&hdr->w);
    const size_t h   = read_le16(&hdr->h);
    const size_t bpp = hdr->bpp;
    const u8 desc  = hdr->img_desc;

    size_t flags = 0;
    flags |= (desc & TGA_TOP_DOWN)? TEX_TOP_DOWN : TEX_BOTTOM_UP;
    if(desc & 0x0F) // alpha bits
        flags |= TEX_ALPHA;
    if(bpp == 8)
        flags |= TEX_GREY;
    if(type == TGA_TRUE_COLOUR)
        flags |= TEX_BGR;

    // sanity checks
    // .. storing right-to-left is just stupid;
    //    we're not going to bother converting it.
    if(desc & TGA_RIGHT_TO_LEFT)
        WARN_RETURN(ERR::TEX_INVALID_LAYOUT);

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


static Status tga_encode(Tex* RESTRICT t, DynArray* RESTRICT da)
{
    u8 img_desc = 0;
    if(t->flags & TEX_TOP_DOWN)
        img_desc |= TGA_TOP_DOWN;
    if(t->bpp == 32)
        img_desc |= 8;  // size of alpha channel
    TgaImgType img_type = (t->flags & TEX_GREY)? TGA_GREY : TGA_TRUE_COLOUR;

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

    const TgaHeader hdr =
    {
        0,              // no image identifier present
        0,              // no colour map present
        (u8)img_type,
        {0,0,0,0,0},    // unused (colour map)
        0, 0,           // unused (origin)
        (u16)t->w,
        (u16)t->h,
        (u8)t->bpp,
        img_desc
    };
    const size_t hdr_size = sizeof(hdr);
    return tex_codec_write(t, transforms, &hdr, hdr_size, da);
}

TEX_CODEC_REGISTER(tga);