- for (int i= 0, iy = ny - 1; iy >= 0; iy--) {
- for (int ix = 0; ix < nx; ix++) {
- int cval = (int) ((v[ix][iy] - pmin) * view_scale);
- if (cval < 0)
- cval = 0;
- else if (cval > 255)
- cval = 255;
- pens[i++] = grayscale[cval];
+ 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);