+#ifdef HAVE_PNG
+void
+ImageFile::writeImagePNG (const char *outfile, int bitdepth, int nxcell, int nycell, double densmin, double densmax)
+{
+ FILE *fp;
+ png_structp png_ptr;
+ png_infop info_ptr;
+ double max_out_level = (1 << bitdepth) - 1;
+ int nx = m_nx;
+ int ny = m_ny;
+ ImageFileArray v = getArray();
+
+ unsigned char* rowp = new unsigned char [nx * nxcell * (bitdepth / 8)];
+
+ if ((fp = fopen (outfile, "wb")) == NULL)
+ return;
+
+ png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+ if (! png_ptr)
+ return;
+
+ info_ptr = png_create_info_struct(png_ptr);
+ if (! info_ptr) {
+ png_destroy_write_struct(&png_ptr, (png_infopp) NULL);
+ fclose(fp);
+ return;
+ }
+
+ if (setjmp(png_ptr->jmpbuf)) {
+ png_destroy_write_struct(&png_ptr, &info_ptr);
+ fclose(fp);
+ return;
+ }
+
+ png_init_io(png_ptr, fp);
+
+ png_set_IHDR(png_ptr, info_ptr, nx * nxcell, ny * nycell, bitdepth, PNG_COLOR_TYPE_GRAY, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_DEFAULT);
+
+ png_write_info(png_ptr, info_ptr);
+ for (int irow = ny - 1; irow >= 0; irow--) {
+ png_bytep row_pointer = rowp;
+
+ for (int icol = 0; icol < nx; icol++) {
+ int pos = icol * nxcell;
+ double dens = (v[icol][irow] - densmin) / (densmax - densmin);
+ dens = clamp (dens, 0., 1.);
+ unsigned int outval = static_cast<unsigned int> (dens * max_out_level);
+
+ for (int p = pos; p < pos + nxcell; p++) {
+ if (bitdepth == 8)
+ rowp[p] = outval;
+ else {
+ int rowpos = p * 2;
+ rowp[rowpos] = (outval >> 8) & 0xFF;
+ rowp[rowpos+1] = (outval & 0xFF);
+ }
+ }
+ }
+ for (int ir = 0; ir < nycell; ir++)
+ png_write_rows (png_ptr, &row_pointer, 1);
+ }
+
+ png_write_end(png_ptr, info_ptr);
+ png_destroy_write_struct(&png_ptr, &info_ptr);
+ delete rowp;\r
+
+ fclose(fp);