263 lines
7 KiB
Python
Executable file
263 lines
7 KiB
Python
Executable file
#!/usr/bin/env python3
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# SPDX-License-Identifier: LGPL-3.0-or-later
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# Copyright (C) 2020 Daniel Thompson
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import argparse
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import sys
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import os.path
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from PIL import Image
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def varname(p):
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return os.path.basename(os.path.splitext(p)[0])
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def encode(im):
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pixels = im.load()
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rle = []
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rl = 0
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px = pixels[0, 0]
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def encode_pixel(px, rl):
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while rl > 255:
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rle.append(255)
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rle.append(0)
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rl -= 255
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rle.append(rl)
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for y in range(im.height):
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for x in range(im.width):
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newpx = pixels[x, y]
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if newpx == px:
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rl += 1
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assert(rl < (1 << 21))
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continue
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# Code the previous run
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encode_pixel(px, rl)
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# Start a new run
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rl = 1
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px = newpx
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# Handle the final run
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encode_pixel(px, rl)
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return (im.width, im.height, bytes(rle))
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def encode_2bit(im):
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"""2-bit palette based RLE encoder.
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This encoder has a reprogrammable 2-bit palette. This allows it to encode
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arbitrary images with a full 8-bit depth but the 2-byte overhead each time
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a new colour is introduced means it is not efficient unless the image is
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carefully constructed to keep a good locality of reference for the three
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non-background colours.
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The encoding competes well with the 1-bit encoder for small monochrome
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images but once run-lengths longer than 62 start to become frequent then
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this encoding is about 30% larger than a 1-bit encoding.
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"""
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pixels = im.load()
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assert(im.width <= 255)
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assert(im.height <= 255)
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rle = []
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rl = 0
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px = pixels[0, 0]
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palette = [0, 0xfc, 0x2d, 0xff]
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next_color = 1
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def encode_pixel(px, rl):
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nonlocal next_color
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px = (px[0] & 0xe0) | ((px[1] & 0xe0) >> 3) | ((px[2] & 0xc0) >> 6)
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if px not in palette:
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rle.append(next_color << 6)
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rle.append(px)
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palette[next_color] = px
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next_color += 1
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if next_color >= len(palette):
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next_color = 1
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px = palette.index(px)
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if rl >= 63:
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rle.append((px << 6) + 63)
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rl -= 63
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while rl >= 255:
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rle.append(255)
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rl -= 255
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rle.append(rl)
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else:
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rle.append((px << 6) + rl)
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# Issue the descriptor
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rle.append(2)
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rle.append(im.width)
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rle.append(im.height)
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for y in range(im.height):
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for x in range(im.width):
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newpx = pixels[x, y]
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if newpx == px:
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rl += 1
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assert(rl < (1 << 21))
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continue
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# Code the previous run
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encode_pixel(px, rl)
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# Start a new run
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rl = 1
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px = newpx
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# Handle the final run
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encode_pixel(px, rl)
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return bytes(rle)
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def encode_8bit(im):
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"""Experimental 8-bit RLE encoder.
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For monochrome images this is about 3x less efficient than the 1-bit
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encoder. This encoder is not currently used anywhere in wasp-os and
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currently there is no decoder either (so don't assume this code
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actually works).
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"""
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pixels = im.load()
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rle = []
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rl = 0
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px = pixels[0, 0]
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def encode_pixel(px, rl):
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px = (px[0] & 0xe0) | ((px[1] & 0xe0) >> 3) | ((px[2] & 0xc0) >> 6)
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rle.append(px)
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if rl > 0:
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rle.append(px)
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rl -= 2
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if rl > (1 << 14):
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rle.append(0x80 | ((rl >> 14) & 0x7f))
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if rl > (1 << 7):
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rle.append(0x80 | ((rl >> 7) & 0x7f))
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if rl >= 0:
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rle.append( rl & 0x7f )
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for y in range(im.height):
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for x in range(im.width):
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newpx = pixels[x, y]
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if newpx == px:
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rl += 1
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assert(rl < (1 << 21))
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continue
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# Code the previous run
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encode_pixel(px, rl)
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# Start a new run
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rl = 1
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px = newpx
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# Handle the final run
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encode_pixel(px, rl)
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return (im.width, im.height, bytes(rle))
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def render_c(image, fname):
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print(f'// 1-bit RLE, generated from {fname}, {len(image[2])} bytes')
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print(f'static const uint8_t {varname(fname)}[] = {{')
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print(' ', end='')
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i = 0
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for rl in image[2]:
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print(f' {hex(rl)},', end='')
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i += 1
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if i == 12:
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print('\n ', end='')
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i = 0
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print('\n};')
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def decode_to_ascii(image):
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(sx, sy, rle) = image
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data = bytearray(2*sx)
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dp = 0
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black = ord('#')
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white = ord(' ')
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color = black
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for rl in rle:
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while rl:
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data[dp] = color
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data[dp+1] = color
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dp += 2
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rl -= 1
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if dp >= (2*sx):
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print(data.decode('utf-8'))
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dp = 0
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if color == black:
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color = white
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else:
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color = black
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# Check the image is the correct length
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assert(dp == 0)
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parser = argparse.ArgumentParser(description='RLE encoder tool.')
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parser.add_argument('files', nargs='+',
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help='files to be encoded')
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parser.add_argument('--ascii', action='store_true',
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help='Run the resulting image(s) through an ascii art decoder')
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parser.add_argument('--c', action='store_true',
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help='Render the output as C instead of python')
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parser.add_argument('--indent', default=0, type=int,
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help='Add extra indentation in the generated code')
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parser.add_argument('--2bit', action='store_true', dest='twobit',
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help='Generate 2-bit image')
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parser.add_argument('--8bit', action='store_true', dest='eightbit',
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help='Generate 8-bit image')
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args = parser.parse_args()
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extra_indent = ' ' * args.indent
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if args.eightbit:
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encoder = encode_8bit
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depth = 8
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elif args.twobit:
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encoder = encode_2bit
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depth = 2
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else:
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encoder = encode
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depth =1
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for fname in args.files:
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image = encoder(Image.open(fname))
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if args.c:
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render_c(image, fname)
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else:
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if len(image) == 3:
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print(f'{extra_indent}# {depth}-bit RLE, generated from {fname}, '
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f'{len(image[2])} bytes')
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(x, y, pixels) = image
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print(f'{extra_indent}{varname(fname)} = (')
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print(f'{extra_indent} {x}, {y},')
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else:
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print(f'{extra_indent}# {depth}-bit RLE, generated from {fname}, '
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f'{len(image)} bytes')
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pixels = image[3:]
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print(f'{extra_indent}{varname(fname)} = (')
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print(f'{extra_indent} {image[0:1]}')
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print(f'{extra_indent} {image[1:3]}')
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# Split the bytestring to ensure each line is short enough to
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# be absorbed on the target if needed.
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for i in range(0, len(pixels), 16):
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print(f'{extra_indent} {pixels[i:i+16]}')
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print(f'{extra_indent})')
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if args.ascii:
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print()
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decode_to_ascii(image)
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