Get list of distinct pixel RGB values

[teapot]

(03-23-2023, 01:28 PM)thetalkietoaster Wrote: Sorry for the very late reply - managed to completely forget about this after I fixed it :/. The code's on GitHub, and it's been revised quite a bit since I posted this. Originally, I was calculating the sum RGB for each pixel and then using that as the dict key, but that was clearly a daft move when I could just do the summing afterwards.

The code I ended up with is below, with changes to account for 1. some palettes having multiple colours of the same sum RGB, and 2. some of the images having 1-2 stray pixels out of the palette. Fixing those meant switching to using pixel RGB as key like you, which then solved the performance issues.

Code:

def extract_sorted_palette(
   layer, include_transparent, count_threshold,
   current_progress, progress_fraction,
):
   """
   Extracts a palette from an image, by finding the discrete RGB values
   and then sorting them by total R+G+B value.
   """
   palette_counts = {}    
   progress_step = progress_fraction / layer.height

   region = layer.get_pixel_rgn(
       0, 0, layer.width, layer.height
   )

   for index_row in range(0, layer.height):
       for pixel in RowIterator(region[0:layer.width, index_row], layer.bpp):
           colour_rgb = pixel[0:3]

           if layer.has_alpha and pixel[3] == 0 and not include_transparent:
               continue

           elif colour_rgb not in palette_counts:
               palette_counts[colour_rgb] = 1

           else:
               palette_counts[colour_rgb] += 1

       gimp.progress_update(current_progress + progress_step * index_row)

   # Now we've counted all the pixel colours, discard outliers and sort
   palette = {}
   for colour_rgb, colour_count in palette_counts.items():
       colour_sum = sum(colour_rgb)

       if colour_count > count_threshold:
           if colour_sum in palette:
               if colour_rgb != palette[colour_sum]:
                   colour_duplicate = palette[colour_sum]
                   raise KeyError(
                       "Multiple colours in layer with same total RGB values: " + \
                       str(colour_rgb) + "(" + str(colour_count) + " pixels) and " + \
                       str(colour_duplicate) + "(" + str(palette_counts[colour_duplicate]) + " pixels). "
                       "Cannot automatically sort colours by brightness. " + \
                       "Try increasing the 'ignore colours with less than this many pixels' setting " + \
                       "to drop stray pixels."
                   )
           else:
               palette[colour_sum] = colour_rgb

   sorted_palette = [
       palette[key] for key in sorted(list(palette.keys()))
   ]
   return sorted_palette

Though looking at your example I can't believe I forgot about defaultdict, I'll fix that. Should also be using actual perceived brightness rather than RGB intensity too.

I just skimmed the function extract_sorted_palette that you pasted into your post compared to your recent github version. Did you mean to change the logic when reversing the if statement:

From:

if layer.has_alpha and pixel[3] == 0 and not include_transparent:
    continue

To:

if include_transparent or layer.has_alpha and pixel[3] > 0:
    up the count

On a brief look, it doesn't seem right for a case when include_transparent is False. Would you be wanting something more like this:

if include_transparent or not layer.has_alpha or pixel[3] > 0:
    up the count