"""Image converter to Apple II Double Hi-Res format.""" import argparse import os.path from typing import Tuple, List from PIL import Image import colour import numpy as np from sklearn import cluster from os import environ environ['PYGAME_HIDE_SUPPORT_PROMPT'] = '1' import pygame import dither as dither_pyx import dither_pattern import image as image_py import palette as palette_py import screen as screen_py # TODO: # - support LR/DLR # - support HGR class ClusterPalette: def __init__( self, image: Image): self._colours_cam = self._image_colours_cam(image) self._errors = [1e9] * 16 self._palettes_cam = np.empty((16, 16, 3), dtype=np.float32) self._palettes_rgb = np.empty((16, 16, 3), dtype=np.float32) self._global_palette = np.empty((16, 16, 3), dtype=np.float32) def _image_colours_cam(self, image: Image): colours_rgb = np.asarray(image).reshape((-1, 3)) with colour.utilities.suppress_warnings(colour_usage_warnings=True): colours_cam = colour.convert(colours_rgb, "RGB", "CAM16UCS").astype(np.float32) return colours_cam def _fit_global_palette(self): """Compute a 16-colour palette for the entire image to use as starting point for the sub-palettes. This should help when the image has large blocks of colour since the sub-palettes will tend to pick the same colours.""" clusters = cluster.MiniBatchKMeans(n_clusters=16, max_iter=10000) clusters.fit_predict(self._colours_cam) return clusters.cluster_centers_ def propose_palettes(self) -> Tuple[np.ndarray, np.ndarray, List[float]]: """Attempt to find new palettes that locally improve image quality. Re-fit a set of 16 palettes from (overlapping) line ranges of the source image, using k-means clustering in CAM16-UCS colour space. We maintain the total image error for the pixels on which the 16 palettes are clustered. A new palette that increases this local image error is rejected. New palettes that reduce local error cannot be applied immediately though, because they may cause an increase in *global* image error when dithering. i.e. they would reduce the overall image quality. The current (locally) best palettes are returned and can be applied using accept_palettes(). """ # Compute a new 16-colour global palette for the entire image, # used as the starting center positions for k-means clustering of the # individual palettes self._global_palette = self._fit_global_palette() new_errors = list(self._errors) new_palettes_cam = np.copy(self._palettes_cam) new_palettes_rgb = np.copy(self._palettes_rgb) # The 16 palettes are striped across consecutive (overlapping) line # ranges. The basic unit is 200/16 = 12.5 lines, but we extend the # line range to cover a multiple of this so that the palette ranges # overlap. Since nearby lines tend to have similar colours, this has # the effect of smoothing out the colour transitions across palettes. palette_band_width = 3 for palette_idx in range(16): p_lower = max(palette_idx + 0.5 - (palette_band_width / 2), 0) p_upper = min(palette_idx + 0.5 + (palette_band_width / 2), 16) # TODO: dynamically tune palette cuts palette_pixels = self._colours_cam[ int(p_lower * (200 / 16)) * 320:int(p_upper * ( 200 / 16)) * 320, :] # TODO: clustering should be aware of the fact that we will # quantize to a 4-bit RGB value afterwards. i.e. we should # not pick multiple centroids that will quantize to the same RGB # value since we'll "waste" a palette entry. This doesn't seem to # be a major issue in practise though, and fixing it would require # implementing our own (optimized) k-means. # TODO: tune tolerance clusters = cluster.MiniBatchKMeans( n_clusters=16, max_iter=10000, init=self._global_palette, n_init=1) clusters.fit_predict(palette_pixels) palette_error = clusters.inertia_ if palette_error >= self._errors[palette_idx]: # Not a local improvement to existing palette continue palette_cam = np.array(clusters.cluster_centers_).astype(np.float32) # Suppress divide by zero warning, # https://github.com/colour-science/colour/issues/900 with colour.utilities.suppress_warnings(python_warnings=True): # SHR colour palette only uses 4-bit RGB values palette_rgb = (np.round(colour.convert( palette_cam, "CAM16UCS", "RGB") * 15) / 15).astype( np.float32) new_palettes_cam[palette_idx, :, :] = palette_cam new_palettes_rgb[palette_idx, :, :] = palette_rgb new_errors[palette_idx] = palette_error return new_palettes_cam, new_palettes_rgb, new_errors def accept_palettes( self, new_palettes_cam: np.ndarray, new_palettes_rgb: np.ndarray, new_errors: List[float]): self._palettes_cam = np.copy(new_palettes_cam) self._palettes_rgb = np.copy(new_palettes_rgb) self._errors = list(new_errors) def main(): parser = argparse.ArgumentParser() parser.add_argument("input", type=str, help="Input image file to process.") parser.add_argument("output", type=str, help="Output file for converted " "Apple II image.") parser.add_argument( "--lookahead", type=int, default=8, help=("How many pixels to look ahead to compensate for NTSC colour " "artifacts (default: 8)")) parser.add_argument( '--dither', type=str, choices=list(dither_pattern.PATTERNS.keys()), default=dither_pattern.DEFAULT_PATTERN, help="Error distribution pattern to apply when dithering (default: " + dither_pattern.DEFAULT_PATTERN + ")") parser.add_argument( '--show-input', action=argparse.BooleanOptionalAction, default=False, help="Whether to show the input image before conversion.") parser.add_argument( '--show-output', action=argparse.BooleanOptionalAction, default=True, help="Whether to show the output image after conversion.") parser.add_argument( '--palette', type=str, choices=list(set(palette_py.PALETTES.keys())), default=palette_py.DEFAULT_PALETTE, help='RGB colour palette to dither to. "ntsc" blends colours over 8 ' 'pixels and gives better image quality on targets that ' 'use/emulate NTSC, but can be substantially slower. Other ' 'palettes determine colours based on 4 pixel sequences ' '(default: ' + palette_py.DEFAULT_PALETTE + ")") parser.add_argument( '--show-palette', type=str, choices=list(palette_py.PALETTES.keys()), help="RGB colour palette to use when --show_output (default: " "value of --palette)") parser.add_argument( '--verbose', action=argparse.BooleanOptionalAction, default=False, help="Show progress during conversion") parser.add_argument( '--gamma_correct', type=float, default=2.4, help='Gamma-correct image by this value (default: 2.4)' ) args = parser.parse_args() if args.lookahead < 1: parser.error('--lookahead must be at least 1') # palette = palette_py.PALETTES[args.palette]() screen = screen_py.SHR320Screen() # Conversion matrix from RGB to CAM16UCS colour values. Indexed by # 24-bit RGB value rgb_to_cam16 = np.load("data/rgb_to_cam16ucs.npy") # Open and resize source image image = image_py.open(args.input) if args.show_input: image_py.resize(image, screen.X_RES, screen.Y_RES, srgb_output=False).show() rgb = np.array( image_py.resize(image, screen.X_RES, screen.Y_RES, gamma=args.gamma_correct)).astype(np.float32) / 255 # TODO: flags penalty = 1e9 iterations = 50 pygame.init() # TODO: for some reason I need to execute this twice - the first time # the window is created and immediately destroyed _ = pygame.display.set_mode((640, 400)) canvas = pygame.display.set_mode((640, 400)) canvas.fill((0, 0, 0)) pygame.display.flip() total_image_error = 1e9 iterations_since_improvement = 0 palette_iigs = np.empty((16, 16, 3), dtype=np.uint8) cluster_palette = ClusterPalette(rgb) while iterations_since_improvement < iterations: new_palettes_cam, new_palettes_rgb, new_palette_errors = ( cluster_palette.propose_palettes()) # Recompute image with proposed palettes and check whether it has # lower total image error than our previous best. new_output_4bit, new_line_to_palette, new_total_image_error = \ dither_pyx.dither_shr( rgb, new_palettes_cam, new_palettes_rgb, rgb_to_cam16, float(penalty)) if new_total_image_error >= total_image_error: iterations_since_improvement += 1 continue # We found a globally better set of palettes iterations_since_improvement = 0 cluster_palette.accept_palettes( new_palettes_cam, new_palettes_rgb, new_palette_errors) if total_image_error < 1e9: print("Improved quality +%f%% (%f)" % ( (1 - new_total_image_error / total_image_error) * 100, new_total_image_error)) output_4bit = new_output_4bit line_to_palette = new_line_to_palette total_image_error = new_total_image_error palettes_rgb = new_palettes_rgb # Recompute 4-bit //gs RGB palettes for i in range(16): palette_iigs[i, :, :] = ( np.round(image_py.linear_to_srgb( palettes_rgb[i, :, :] * 255) / 255 * 15)).astype(np.uint8) screen.set_palette(i, palette_iigs[i, :, :]) # Recompute current screen RGB image screen.set_pixels(output_4bit) output_rgb = np.empty((200, 320, 3), dtype=np.uint8) for i in range(200): screen.line_palette[i] = line_to_palette[i] output_rgb[i, :, :] = ( palettes_rgb[line_to_palette[i]][ output_4bit[i, :]] * 255).astype(np.uint8) output_srgb = image_py.linear_to_srgb(output_rgb).astype(np.uint8) # dither = dither_pattern.PATTERNS[args.dither]() # bitmap = dither_pyx.dither_image( # screen, rgb, dither, args.lookahead, args.verbose, rgb_to_cam16) # Show output image by rendering in target palette # output_palette_name = args.show_palette or args.palette # output_palette = palette_py.PALETTES[output_palette_name]() # output_screen = screen_py.DHGRScreen(output_palette) # if output_palette_name == "ntsc": # output_srgb = output_screen.bitmap_to_image_ntsc(bitmap) # else: # output_srgb = image_py.linear_to_srgb( # output_screen.bitmap_to_image_rgb(bitmap)).astype(np.uint8) out_image = image_py.resize( Image.fromarray(output_srgb), screen.X_RES * 2, screen.Y_RES * 2, srgb_output=True) if args.show_output: surface = pygame.surfarray.make_surface( np.asarray(out_image).transpose((1, 0, 2))) # flip y/x axes canvas.blit(surface, (0, 0)) pygame.display.flip() unique_colours = np.unique(palette_iigs.reshape(-1, 3), axis=0).shape[0] print("%d unique colours" % unique_colours) # Save Double hi-res image outfile = os.path.join(os.path.splitext(args.output)[0] + "-preview.png") out_image.save(outfile, "PNG") screen.pack() # with open(args.output, "wb") as f: # f.write(bytes(screen.aux)) # f.write(bytes(screen.main)) with open(args.output, "wb") as f: f.write(bytes(screen.memory)) if __name__ == "__main__": main()