source: nanovis/trunk/imgLoaders/BMPImageLoaderImpl.cpp @ 4923

/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#include <stdio.h>
#include <memory.h>
#include <stdlib.h>

#include "BMPImageLoaderImpl.h"
#include "Image.h"
#include "Trace.h"

BMPImageLoaderImpl::BMPImageLoaderImpl()
{
}

BMPImageLoaderImpl::~BMPImageLoaderImpl()
{
}

// I referred to cjbackhouse@hotmail.com                www.backhouse.tk
Image *BMPImageLoaderImpl::load(const char *fileName)
{
    TRACE("BMP loader\n");
    Image *image = NULL;

    TRACE("opening image file \"%s\"\n", fileName);
    FILE *f = fopen(fileName, "rb");

    if (!f)  {
        TRACE("File not found\n");
        return 0;
    }

    char header[54];
    if (fread(&header, 54, 1, f) != 1) {
        TRACE("can't read header of BMP file\n");
        return 0;
    }

    if (header[0] != 'B' ||  header[1] != 'M') {
        TRACE("File is not BMP format\n");
        return 0;
    }

    //it seems gimp sometimes makes its headers small, so we have to do
    //this. hence all the fseeks
    int offset = *(unsigned int*)(header+10);

    const unsigned int width = *(int*)(header+18);
    const unsigned int height = *(int*)(header+22);

    int bits = int(header[28]);           //colourdepth

    TRACE("image width = %d height = %d bits=%d\n", width, height, bits);

    image = new Image(width, height, _targetImageFormat, 
                      Image::IMG_UNSIGNED_BYTE, NULL);

    TRACE("image created\n");

    unsigned char *bytes = (unsigned char *)image->getImageBuffer();
    memset(bytes, 0, sizeof(unsigned char) * width * height * _targetImageFormat);

    TRACE("reset image buffer\n");

    unsigned int x, y;
    unsigned char cols[256*4];  //colourtable
    switch (bits) {
    case 24:
        fseek(f, offset, SEEK_SET);
        if (_targetImageFormat == Image::IMG_RGB) {
            if (fread(bytes, width*height*3, 1, f) != 1) {
                ERROR("can't read image data\n");
            }
            for (x = 0; x < width*height*3; x += 3)  { //except the format is BGR, grr
                unsigned char temp = bytes[x];
                bytes[x] = bytes[x+2];
                bytes[x+2] = temp;
            }
        } else if (_targetImageFormat == Image::IMG_RGBA) {
            unsigned char *buff = (unsigned char*)malloc(width * height * sizeof(unsigned char) * 3);
            if (fread(buff, width*height*3, 1, f) != 1) {
                ERROR("can't read BMP image data\n");
            }
            for (x = 0, y = 0; x < width*height*3; x += 3, y += 4) {       //except the format is BGR, grr
                bytes[y] = buff[x+2];
                bytes[y+1] = buff[x+1];
                bytes[y+2] = buff[x];
                bytes[y+3] = 255;
            }
            free(buff);
        }
        break;
    case 32:
        fseek(f, offset, SEEK_SET);
        if (_targetImageFormat == Image::IMG_RGBA) {
            if (fread(bytes, width*height*4, 1, f) != 1) {
                ERROR("can't read image data\n");
            }
            for (x = 0; x < width*height*4; x += 4)  { //except the format is BGR, grr
                unsigned char temp = bytes[x];
                bytes[x] = bytes[x+2];
                bytes[x+2] = temp;
            }
        } else if (_targetImageFormat == Image::IMG_RGB) {
            unsigned char *buff = (unsigned char*)malloc(width * height * sizeof(unsigned char) * 4);
            if (fread(buff, width*height*4, 1, f) != 1) {
                ERROR("can't read BMP image data\n");
            }
            for (x = 0, y = 0; x < width*height*4; x += 4, y += 3) {       //except the format is BGR, grr
                bytes[y] = buff[x+2];
                bytes[y+1] = buff[x+1];
                bytes[y+2] = buff[x];
            }
            free(buff);
        }
        break;
    case 8:
        if (fread(cols, 256 * 4, 1, f) != 1) {
            ERROR("can't read colortable from BMP file\n");
        }
        fseek(f,offset,SEEK_SET);  
        for (y = 0; y < height; ++y) {  //(Notice 4bytes/col for some reason)
            for (x = 0; x < width; ++x) {
                unsigned char byte;                 
                if (fread(&byte, 1, 1, f) != 1) {
                    ERROR("error reading BMP file\n");
                }
                for (int c = 0; c < 3; ++c) {
                    //bytes[(y*width+x)*3+c] = cols[byte*4+2-c];        //and look up in the table 
                    bytes[(y*width+x)*_targetImageFormat + c] = cols[byte*4+2-c];       //and look up in the table
                }
                if (_targetImageFormat == Image::IMG_RGBA) {
                    bytes[(y*width+x)*_targetImageFormat + 3] = 255;
                }
            }
        }
        break;
    }

    TRACE("image initialized\n");
    return image;
}