How exactly do I get zoom level in GUI?

Software G'MIC
2

For this, use these pre-defined variables:

  • $_preview_x0: X-coordinate of the upper-left corner of the preview (expressed in the image space).
  • $_preview_y0: Y-coordinate of the upper-left corner of the preview (exressed in the image space).
  • $_preview_x1: X-coordinate of the lower-right corner of the preview (expressed in the image space).
  • $_preview_y1: Y-coordinate of the lower-right corner of the preview (expressed in the image space).