packmap.cc

#include <gdal_priv.h>
#include <cpl_conv.h>
#include <stdio.h>

uint32_t htonf(float f){
  uint32_t p;
  uint32_t sign = 0;

  if (f < 0) { f = 0; } // floor

  p = ((((uint32_t)f)&0x7fff)<<16) | (sign<<31); // whole part and sign
  p |= (uint32_t)(((f - (int)f) * 65536.0f))&0xffff; // fraction

  return p;
}


int main(int argc, char **argv){
  if(argc != 3) {
    puts("Usage: packmap <gray_valued_raster> <out>");
    exit(1);
  }

  GDALAllRegister();
  GDALDataset *dataset = (GDALDataset *) GDALOpen(argv[1], GA_ReadOnly);
  if(dataset == NULL) { printf("couldn't open %s", argv[1]); exit(1); }
  GDALRasterBand *band = dataset->GetRasterBand(1);

  int xSize = band->GetXSize(), ySize = band->GetYSize();

  float *scanline = (float *) CPLMalloc(sizeof(float)*xSize);

  GDALDriver *driver = GetGDALDriverManager()->GetDriverByName("GTiff");

  GDALDataset *outDS = driver->Create(argv[2], xSize, ySize, 4, GDT_Byte, NULL);

  GDALRasterBand *aband = outDS->GetRasterBand(4);

  for(int y = 0; y < ySize; y++) {
    band->RasterIO(GF_Read, 0, y, xSize, 1, scanline, xSize, 1, band->GetRasterDataType(), 0, 0);

    for(int x = 0; x < xSize; x++) {
      uint32_t i1 = htonf(scanline[x]);

      for(int i = 1; i <= 4; i++){
        GDALRasterBand *band = outDS->GetRasterBand(i);
        // HACCCCCKKKZZZZZZ
        char* it = ((char*)&i1);
        band->RasterIO(GF_Write, x, y, 1, 1, &(it[i - 1]), 1, 1, GDT_Byte, 0, 0);
      }
    }

  }

  GDALClose((GDALDatasetH) dataset);
  GDALClose((GDALDatasetH) outDS);
}