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tga_image.cpp

//FILE:         tga_image.cpp
//AUTHOR:       Nathan Cournia <nathan@cournia.com>

#include <fstream>
#include "utils.h"
#include "tga_image.h"

image::image_t*
image::tga::load( const std::string& filename )
{
        //open file
        std::ifstream stream( filename.c_str( ) );
        if( !stream ) {
                //could not open file
                return NULL;
        }

        //load the file
        image_t* img = load( stream );

        //close the file
        stream.close( );

        //return the image
        return img;
}

image::image_t*
image::tga::load( std::istream& stream )
{
        //read in header
        header_t header;
        if( !utils::read( stream, header ) ) {
                //could not read header
                return NULL;
        }

        //make sure this is a tga we like
        if(     (header.id_length != 0) ||
                (header.color_map_type != 0) || //no colormap
                (header.image_type != 2) ||     //true color
                (header.x_origin != 0) ||       //origin in bottom left
                (header.y_origin != 0) ) {      //origin in bottom left
                //we can't read the image
                return false;
        }

        //check bits per pixel to get format
        image_t::format format;
        if( header.bpp == 24 ) {
                format = image_t::RGB;
        } else if( header.bpp == 32 ) {
                format = image_t::RGBA;
        }

        //allocate image
        image_t *img = new image_t( header.width, header.height, format, 
                image_t::BYTE );
        img->seek( 0, 0 );

        //read in image
        unsigned int pixels = header.width * header.height;

        if( format == image_t::RGB ) {
                char r, g, b;
                for( unsigned int i = 0; i < pixels; ++i ) {
                        if( !(stream.read( &b, 1 ) &&
                                stream.read( &g, 1 ) &&
                                stream.read( &r, 1 )) ) {
                                //either not enough data, or corrupt data
                                delete img;
                                return NULL;
                        }

                        //set pixel
                        img->write( r, g, b );
                }
        } else {
                char r, g, b, a;
                for( unsigned int i = 0; i < pixels; ++i ) {
                        if( !(stream.read( &b, 1 ) &&
                                stream.read( &g, 1 ) &&
                                stream.read( &r, 1 ) &&
                                stream.read( &a, 1 )) ) {
                                //either not enough data, or corrupt data
                                delete img;
                                return NULL;
                        }

                        //set pixel
                        img->write( r, g, b, a );
                }
        }

        return img;

}

bool
image::tga::can_load( const std::string& filename )
{
        //open file
        std::ifstream stream( filename.c_str( ) );
        if( !stream ) {
                //could not open file
                return false;
        }

        //load the file
        bool loadable = can_load( stream );

        //close the file
        stream.close( );

        //return status
        return loadable;
}

bool
image::tga::can_load( std::istream& stream )
{
        //save current position in stream
        std::streampos save = stream.tellg( );

        //read in header
        header_t header;
        if( !utils::read( stream, header ) ) {
                //could not read header
                //return current position to saved value
                stream.seekg( save );
                return false;
        }

        //return current position to saved value
        stream.seekg( save );

        //make sure this is a tga we like
        if(     (header.id_length != 0) ||
                (header.color_map_type != 0) || //no colormap
                (header.image_type != 2) ||     //true color
                (header.x_origin != 0) ||       //origin in bottom left
                (header.y_origin != 0) ) {      //origin in bottom left
                //we can't read the image
                return false;
        }

        //we'll probably be able to read the image
        return true;
}

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