//========================================================================
// GLFW - An OpenGL framework
// File:        tga.c
// Platform:    Any
// API version: 2.7
// WWW:         http://glfw.sourceforge.net
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Camilla Berglund
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would
//    be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
//    be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
//    distribution.
//
//========================================================================

//========================================================================
// Description:
//
// TGA format image file loader. This module supports version 1 Targa
// images, with these restrictions:
//  - Pixel format may only be 8, 24 or 32 bits
//  - Colormaps must be no longer than 256 entries
//
//========================================================================


#include "internal.h"


//************************************************************************
//****            GLFW internal functions & declarations              ****
//************************************************************************

//========================================================================
// TGA file header information
//========================================================================

typedef struct {
    int idlen;                 // 1 byte
    int cmaptype;              // 1 byte
    int imagetype;             // 1 byte
    int cmapfirstidx;          // 2 bytes
    int cmaplen;               // 2 bytes
    int cmapentrysize;         // 1 byte
    int xorigin;               // 2 bytes
    int yorigin;               // 2 bytes
    int width;                 // 2 bytes
    int height;                // 2 bytes
    int bitsperpixel;          // 1 byte
    int imageinfo;             // 1 byte
    int _alphabits;            // (derived from imageinfo)
    int _origin;               // (derived from imageinfo)
} _tga_header_t;

#define _TGA_CMAPTYPE_NONE      0
#define _TGA_CMAPTYPE_PRESENT   1

#define _TGA_IMAGETYPE_NONE     0
#define _TGA_IMAGETYPE_CMAP     1
#define _TGA_IMAGETYPE_TC       2
#define _TGA_IMAGETYPE_GRAY     3
#define _TGA_IMAGETYPE_CMAP_RLE 9
#define _TGA_IMAGETYPE_TC_RLE   10
#define _TGA_IMAGETYPE_GRAY_RLE 11

#define _TGA_IMAGEINFO_ALPHA_MASK   0x0f
#define _TGA_IMAGEINFO_ALPHA_SHIFT  0
#define _TGA_IMAGEINFO_ORIGIN_MASK  0x30
#define _TGA_IMAGEINFO_ORIGIN_SHIFT 4

#define _TGA_ORIGIN_BL 0
#define _TGA_ORIGIN_BR 1
#define _TGA_ORIGIN_UL 2
#define _TGA_ORIGIN_UR 3


//========================================================================
// _glfwReadTGAHeader() - Read TGA file header (and check that it is
// valid)
//========================================================================

static int ReadTGAHeader( _GLFWstream *s, _tga_header_t *h )
{
    unsigned char buf[ 18 ];
    int pos;

    // Read TGA file header from file
    pos = _glfwTellStream( s );
    _glfwReadStream( s, buf, 18 );

    // Interpret header (endian independent parsing)
    h->idlen         = (int) buf[0];
    h->cmaptype      = (int) buf[1];
    h->imagetype     = (int) buf[2];
    h->cmapfirstidx  = (int) buf[3] | (((int) buf[4]) << 8);
    h->cmaplen       = (int) buf[5] | (((int) buf[6]) << 8);
    h->cmapentrysize = (int) buf[7];
    h->xorigin       = (int) buf[8] | (((int) buf[9]) << 8);
    h->yorigin       = (int) buf[10] | (((int) buf[11]) << 8);
    h->width         = (int) buf[12] | (((int) buf[13]) << 8);
    h->height        = (int) buf[14] | (((int) buf[15]) << 8);
    h->bitsperpixel  = (int) buf[16];
    h->imageinfo     = (int) buf[17];

    // Extract alphabits and origin information
    h->_alphabits = (int) (h->imageinfo & _TGA_IMAGEINFO_ALPHA_MASK) >>
                     _TGA_IMAGEINFO_ALPHA_SHIFT;
    h->_origin    = (int) (h->imageinfo & _TGA_IMAGEINFO_ORIGIN_MASK) >>
                     _TGA_IMAGEINFO_ORIGIN_SHIFT;

    // Validate TGA header (is this a TGA file?)
    if( (h->cmaptype == 0 || h->cmaptype == 1) &&
        ((h->imagetype >= 1 && h->imagetype <= 3) ||
         (h->imagetype >= 9 && h->imagetype <= 11)) &&
         (h->bitsperpixel == 8 || h->bitsperpixel == 24 ||
          h->bitsperpixel == 32) )
    {
        // Skip the ID field
        _glfwSeekStream( s, h->idlen, SEEK_CUR );

        // Indicate that the TGA header was valid
        return GL_TRUE;
    }
    else
    {
        // Restore file position
        _glfwSeekStream( s, pos, SEEK_SET );

        // Indicate that the TGA header was invalid
        return GL_FALSE;
    }
}

//========================================================================
// Read Run-Length Encoded data
//========================================================================

static void ReadTGA_RLE( unsigned char *buf, int size, int bpp,
    _GLFWstream *s )
{
    int repcount, bytes, k, n;
    unsigned char pixel[ 4 ];
    char c;

    // Dummy check
    if( bpp > 4 )
    {
        return;
    }

    while( size > 0 )
    {
        // Get repetition count
	_glfwReadStream( s, &c, 1 );
        repcount = (unsigned int) c;
        bytes = ((repcount & 127) + 1) * bpp;
        if( size < bytes )
        {
            bytes = size;
        }

        // Run-Length packet?
        if( repcount & 128 )
        {
            _glfwReadStream( s, pixel, bpp );
            for( n = 0; n < (repcount & 127) + 1; n ++ )
            {
                for( k = 0; k < bpp; k ++ )
                {
                    *buf ++ = pixel[ k ];
                }
            }
        }
        else
        {
            // It's a Raw packet
            _glfwReadStream( s, buf, bytes );
            buf += bytes;
        }

        size -= bytes;
    }
}


//========================================================================
// _glfwReadTGA() - Read a TGA image from a file
//========================================================================

int _glfwReadTGA( _GLFWstream *s, GLFWimage *img, int flags )
{
    _tga_header_t h;
    unsigned char *cmap, *pix, tmp, *src, *dst;
    int cmapsize, pixsize, pixsize2;
    int bpp, bpp2, k, m, n, swapx, swapy;

    // Read TGA header
    if( !ReadTGAHeader( s, &h ) )
    {
        return 0;
    }

    // Is there a colormap?
    cmapsize = (h.cmaptype == _TGA_CMAPTYPE_PRESENT ? 1 : 0) * h.cmaplen *
               ((h.cmapentrysize+7) / 8);
    if( cmapsize > 0 )
    {
        // Is it a colormap that we can handle?
        if( (h.cmapentrysize != 24 && h.cmapentrysize != 32) ||
            h.cmaplen == 0 || h.cmaplen > 256 )
        {
            return 0;
        }

        // Allocate memory for colormap
        cmap = (unsigned char *) malloc( cmapsize );
        if( cmap == NULL )
        {
            return 0;
        }

        // Read colormap from file
        _glfwReadStream( s, cmap, cmapsize );
    }
    else
    {
        cmap = NULL;
    }

    // Size of pixel data
    pixsize = h.width * h.height * ((h.bitsperpixel + 7) / 8);

    // Bytes per pixel (pixel data - unexpanded)
    bpp = (h.bitsperpixel + 7) / 8;

    // Bytes per pixel (expanded pixels - not colormap indeces)
    if( cmap )
    {
        bpp2 = (h.cmapentrysize + 7) / 8;
    }
    else
    {
        bpp2 = bpp;
    }

    // For colormaped images, the RGB/RGBA image data may use more memory
    // than the stored pixel data
    pixsize2 = h.width * h.height * bpp2;

    // Allocate memory for pixel data
    pix = (unsigned char *) malloc( pixsize2 );
    if( pix == NULL )
    {
        if( cmap )
        {
            free( cmap );
        }
        return 0;
    }

    // Read pixel data from file
    if( h.imagetype >= _TGA_IMAGETYPE_CMAP_RLE )
    {
        ReadTGA_RLE( pix, pixsize, bpp, s );
    }
    else
    {
        _glfwReadStream( s, pix, pixsize );
    }

    // If the image origin is not what we want, re-arrange the pixels
    switch( h._origin )
    {
    default:
    case _TGA_ORIGIN_UL:
        swapx = 0;
        swapy = 1;
        break;

    case _TGA_ORIGIN_BL:
        swapx = 0;
        swapy = 0;
        break;

    case _TGA_ORIGIN_UR:
        swapx = 1;
        swapy = 1;
        break;

    case _TGA_ORIGIN_BR:
        swapx = 1;
        swapy = 0;
        break;
    }
    if( (swapy && !(flags & GLFW_ORIGIN_UL_BIT)) ||
        (!swapy && (flags & GLFW_ORIGIN_UL_BIT)) )
    {
        src = pix;
        dst = &pix[ (h.height-1)*h.width*bpp ];
        for( n = 0; n < h.height/2; n ++ )
        {
            for( m = 0; m < h.width ; m ++ )
            {
                for( k = 0; k < bpp; k ++ )
                {
                    tmp     = *src;
                    *src ++ = *dst;
                    *dst ++ = tmp;
                }
            }
            dst -= 2*h.width*bpp;
        }
    }
    if( swapx )
    {
        src = pix;
        dst = &pix[ (h.width-1)*bpp ];
        for( n = 0; n < h.height; n ++ )
        {
            for( m = 0; m < h.width/2 ; m ++ )
            {
                for( k = 0; k < bpp; k ++ )
                {
                    tmp     = *src;
                    *src ++ = *dst;
                    *dst ++ = tmp;
                }
                dst -= 2*bpp;
            }
            src += ((h.width+1)/2)*bpp;
            dst += ((3*h.width+1)/2)*bpp;
        }
    }

    // Convert BGR/BGRA to RGB/RGBA, and optionally colormap indeces to
    // RGB/RGBA values
    if( cmap )
    {
        // Convert colormap pixel format (BGR -> RGB or BGRA -> RGBA)
        if( bpp2 == 3 || bpp2 == 4 )
        {
            for( n = 0; n < h.cmaplen; n ++ )
            {
                tmp                = cmap[ n*bpp2 ];
                cmap[ n*bpp2 ]     = cmap[ n*bpp2 + 2 ];
                cmap[ n*bpp2 + 2 ] = tmp;
            }
        }

        // Convert pixel data to RGB/RGBA data
        for( m = h.width * h.height - 1; m >= 0; m -- )
        {
            n = pix[ m ];
            for( k = 0; k < bpp2; k ++ )
            {
                pix[ m*bpp2 + k ] = cmap[ n*bpp2 + k ];
            }
        }

        // Free memory for colormap (it's not needed anymore)
        free( cmap );
    }
    else
    {
        // Convert image pixel format (BGR -> RGB or BGRA -> RGBA)
        if( bpp2 == 3 || bpp2 == 4 )
        {
            src = pix;
            dst = &pix[ 2 ];
            for( n = 0; n < h.height * h.width; n ++ )
            {
                tmp  = *src;
                *src = *dst;
                *dst = tmp;
                src += bpp2;
                dst += bpp2;
            }
        }
    }

    // Fill out GLFWimage struct (the Format field will be set by
    // glfwReadImage)
    img->Width         = h.width;
    img->Height        = h.height;
    img->BytesPerPixel = bpp2;
    img->Data          = pix;

    return 1;
}