we should have proper global colormap support for animated GIF from multiple images.

[ChrisBarker-NOAA]

Within PyGNOMe, we do a coloramp to set various colors for drawing elements at different depths.

This is working fine for PNG images, but not for animated GIF. ???

Example code:

        cr = py_gd.color_ramp.ColorRamp(color_scheme,
                                            min_val, max_val,
                                            base_colorscheme=len(existing_colors))
        self.fore_image.add_colors(cr.colorlist)
        self.back_image.add_colors(cr.colorlist)

then:

            if self.depth_colors is not None:
                print("getting colors")
                color = self._color_ramp.get_color_indices(points_in_water[:, 2])
                print(color)

            self.draw_points(points_in_water,
                             diameter=self.point_size,
                             color=color,
                             shape="round")

which then calls:

            img.draw_dots(points, diameter=diameter, color=color)

Hmm -- maybe the problem is that the Animation add_frame is not using the colorramp??

[ChrisBarker-NOAA]

Turns out that the issue is that if you use a different image (rather than clearing a re-using one) for each frame, then the palette does get set right.

This can be worked around by setting:

global_colormap=0

which will then correctly use the proper palette for each frame.

However, it should be possible to use different images, but the same palette -- so it would be good to fix that.

libgd has a call to do that:

Setting the LocalCM flag to 1 adds a local palette for this image to the animation. Otherwise the global palette is assumed and the user must make sure the palettes match. Use gdImagePaletteCopy to do that.

re-titled this issue to keep it around.