prog8/scripts/cx16images.py

"""
Tools to convert bitmap images to an appropriate format for the Commander X16.
This means: indexed colors (palette), 12 bits color space (4 bits per channel, for a total of 4096 possible colors)
There are no restrictions on the size of the image.

Written by Irmen de Jong (irmen@razorvine.net) - Code is in the Public Domain.

Requirements: Pillow  (pip install pillow)
"""

from PIL import Image, PyAccess
from typing import TypeAlias

RGBList: TypeAlias = list[tuple[int, int, int]]

# the 256 default colors of the Commander X16's color palette in (r,g,b) format
default_colors = []

_colors="""000,fff,800,afe,c4c,0c5,00a,ee7,d85,640,f77,333,777,af6,08f,bbb
000,111,222,333,444,555,666,777,888,999,aaa,bbb,ccc,ddd,eee,fff
211,433,644,866,a88,c99,fbb,211,422,633,844,a55,c66,f77,200,411
611,822,a22,c33,f33,200,400,600,800,a00,c00,f00,221,443,664,886
aa8,cc9,feb,211,432,653,874,a95,cb6,fd7,210,431,651,862,a82,ca3
fc3,210,430,640,860,a80,c90,fb0,121,343,564,786,9a8,bc9,dfb,121
342,463,684,8a5,9c6,bf7,120,241,461,582,6a2,8c3,9f3,120,240,360
480,5a0,6c0,7f0,121,343,465,686,8a8,9ca,bfc,121,242,364,485,5a6
6c8,7f9,020,141,162,283,2a4,3c5,3f6,020,041,061,082,0a2,0c3,0f3
122,344,466,688,8aa,9cc,bff,122,244,366,488,5aa,6cc,7ff,022,144
166,288,2aa,3cc,3ff,022,044,066,088,0aa,0cc,0ff,112,334,456,668
88a,9ac,bcf,112,224,346,458,56a,68c,79f,002,114,126,238,24a,35c
36f,002,014,016,028,02a,03c,03f,112,334,546,768,98a,b9c,dbf,112
324,436,648,85a,96c,b7f,102,214,416,528,62a,83c,93f,102,204,306
408,50a,60c,70f,212,434,646,868,a8a,c9c,fbe,211,423,635,847,a59
c6b,f7d,201,413,615,826,a28,c3a,f3c,201,403,604,806,a08,c09,f0b"""

for line in _colors.splitlines():
    for rgb in line.split(","):
        r = int(rgb[0], 16)
        g = int(rgb[1], 16)
        b = int(rgb[2], 16)
        default_colors.append((r, g, b))


class BitmapImage:
    def __init__(self, filename: str, image: Image = None) -> None:
        """Just load the given bitmap image file (any format allowed)."""
        if image is not None:
            self.img = image
        else:
            self.img = Image.open(filename)
        self.size = self.img.size
        self.width, self.height = self.size

    def save(self, filename: str) -> None:
        """Save the image to a new file, format based on the file extension."""
        self.img.save(filename)

    def get_image(self) -> Image:
        """Gets access to a copy of the Pillow Image class that holds the loaded image"""
        return self.img.copy()

    def crop(self, x, y, width, height) -> "BitmapImage":
        """Returns a rectangle cropped from the original image"""
        cropped = self.img.crop((x, y, x + width, y + height))
        return BitmapImage("", cropped)

    def has_palette(self) -> bool:
        """Is it an indexed colors image?"""
        return self.img.mode == "P"

    def get_palette(self) -> RGBList:
        """Return the image's palette as a list of (r,g,b) tuples"""
        return flat_palette_to_rgb(self.img.getpalette())

    def get_vera_palette(self) -> bytes:
        """
        Returns the image's palette as GB0R words (RGB in little-endian), suitable for the Vera palette registers.
        The palette must be in 12 bit color space already! Because this routine just takes the upper 4 bits of every channel value.
        """
        return rgb_palette_to_vera(self.get_palette())

    def show(self) -> None:
        """Shows the image on the screen"""
        if self.img.mode == "P":
            self.img.convert("RGB").convert("P").show()
        else:
            self.img.show()

    def get_pixels_8bpp(self, x: int, y: int, width: int, height: int) -> bytearray:
        """
        For 8 bpp (256 color) images:
        Get a rectangle of pixel values from the image, returns the bytes as a flat array
        """
        assert self.has_palette()
        try:
            access = PyAccess.new(self.img, readonly=True)
        except AttributeError:
            access = self.img
        data = bytearray(width * height)
        index = 0
        for py in range(y, y + height):
            for px in range(x, x + width):
                data[index] = access.getpixel((px, py))
                index += 1
        return data

    def get_all_pixels_8bpp(self) -> bytes:
        """
        For 8 bpp (256 color) images:
        Get all pixel values from the image, returns the bytes as a flat array
        """
        assert self.has_palette()
        return self.img.tobytes()
        # try:
        #     access = PyAccess.new(self.img, readonly=True)
        # except AttributeError:
        #     access = self.img
        # data = bytearray(self.width * self.height)
        # index = 0
        # for py in range(self.height):
        #     for px in range(self.width):
        #         data[index] = access.getpixel((px, py))
        #         index += 1
        # return data

    def get_pixels_4bpp(self, x: int, y: int, width: int, height: int) -> bytearray:
        """
        For 4 bpp (16 color) images:
        Get a rectangle of pixel values from the image, returns the bytes as a flat array.
        Every byte encodes 2 pixels (4+4 bits).
        """
        assert self.has_palette()
        try:
            access = PyAccess.new(self.img, readonly=True)
        except AttributeError:
            access = self.img
        data = bytearray(width // 2 * height)
        index = 0
        for py in range(y, y + height):
            for px in range(x, x + width, 2):
                pix1 = access.getpixel((px, py))
                pix2 = access.getpixel((px + 1, py))
                data[index] = pix1 << 4 | pix2
                index += 1
        return data

    def get_all_pixels_4bpp(self) -> bytearray:
        """
        For 4 bpp (16 color) images:
        Get all pixel values from the image, returns the bytes as a flat array.
        Every byte encodes 2 pixels (4+4 bits).
        """
        assert self.has_palette()
        try:
            access = PyAccess.new(self.img, readonly=True)
        except AttributeError:
            access = self.img
        data = bytearray(self.width // 2 * self.height)
        index = 0
        for py in range(self.height):
            for px in range(0, self.width, 2):
                pix1 = access.getpixel((px, py))
                pix2 = access.getpixel((px + 1, py))
                data[index] = pix1 << 4 | pix2
                index += 1
        return data

    def quantize_to(self, palette_rgb12: RGBList, dither: Image.Dither = Image.Dither.FLOYDSTEINBERG) -> None:
        """
        Convert the image to one with the supplied palette.
        This palette must be in 12 bits colorspace (4 bits so 0-15 per channel)
        The resulting image will have its palette extended to 8 bits per channel again.
        If you want to display the image on the actual Commander X16, simply take the lower (or upper) 4 bits of every color channel.
        Dithering is applied as given (default is Floyd-Steinberg).
        """
        palette_image = Image.new("P", (1, 1))
        palette = []
        for r, g, b in palette_rgb12:
            palette.append(r << 4 | r)
            palette.append(g << 4 | g)
            palette.append(b << 4 | b)
        palette_image.putpalette(palette)
        self.img = self.img.quantize(dither=dither, palette=palette_image)

    def quantize(self, bits_per_pixel: int, preserve_first_16_colors: bool,
                 dither: Image.Dither = Image.Dither.FLOYDSTEINBERG) -> None:
        """
        Convert the image to one with indexed colors (12 bits colorspace palette extended back into 8 bits per channel).
        If you want to display the image on the actual Commander X16, simply take the lower (or upper) 4 bits of every color channel.
        There is support for either 8 or 4 bits per pixel (256 or 16 color modes).
        Dithering is applied as given (default is Floyd-Steinberg).
        """
        if bits_per_pixel == 8:
            num_colors = 240 if preserve_first_16_colors else 256
        elif bits_per_pixel == 4:
            num_colors = 16
            if preserve_first_16_colors:
                return self.quantize_to(default_colors[:16])
        elif bits_per_pixel == 2:
            assert preserve_first_16_colors==False, "bpp is too small for 16 default colors"
            num_colors = 4
        elif bits_per_pixel == 1:
            assert preserve_first_16_colors==False, "bpp is too small for 16 default colors"
            num_colors = 2
        else:
            raise ValueError("only 8,4,2,1 bpp supported")
        image = self.img.convert("RGB")
        palette_image = image.quantize(colors=num_colors, dither=Image.Dither.NONE, method=Image.Quantize.MAXCOVERAGE)
        if len(palette_image.getpalette()) // 3 > num_colors:
            palette_image = image.quantize(colors=num_colors - 1, dither=Image.Dither.NONE, method=Image.Quantize.MAXCOVERAGE)
        palette_rgb = flat_palette_to_rgb(palette_image.getpalette())
        palette_rgb = list(reversed(sorted(set(palette_8to4(palette_rgb)))))
        if preserve_first_16_colors:
            palette_rgb = default_colors[:16] + palette_rgb
        self.img = image
        self.quantize_to(palette_rgb, dither)

    def constrain_size(self, hires: bool = False) -> None:
        """
        If the image is larger than the lores or hires screen size, scale it down so that it fits.
        If the image already fits, doesn't do anything.
        """
        w, h = self.img.size
        if hires and (w > 640 or h > 480):
            self.img.thumbnail((640, 480))
        elif w > 320 or h > 240:
            self.img.thumbnail((320, 240))
        self.size = self.img.size
        self.width, self.height = self.size


# utility functions

def channel_8to4(color: int) -> int:
    """Accurate conversion of a single 8 bit color channel value to 4 bits"""
    return (color * 15 + 135) >> 8  # see https://threadlocalmutex.com/?p=48


def palette_8to4(palette_rgb: RGBList) -> RGBList:
    """Accurate conversion of a 24 bits palette (8 bits per channel) to a 12 bits palette (4 bits per channel)"""
    converted = []
    for ci in range(len(palette_rgb)):
        r, g, b = palette_rgb[ci]
        converted.append((channel_8to4(r), channel_8to4(g), channel_8to4(b)))
    return converted


def reduce_colorspace(palette_rgb: RGBList) -> RGBList:
    """
    Convert 24 bits color space (8 bits per channel) to 12 bits color space (4 bits per channel).
    The resulting color values are still full 8 bits but their precision is reduced.
    You can take either the upper or lower 4 bits of each channel byte to get the actual 4 bits precision.
    """
    converted = []
    for r, g, b in palette_rgb:
        r = channel_8to4(r)
        g = channel_8to4(g)
        b = channel_8to4(b)
        converted.append((r << 4 | r, g << 4 | g, b << 4 | b))
    return converted


def flat_palette_to_rgb(palette: list[int]) -> RGBList:
    """Converts the flat palette list usually obtained from Pillow images to a list of (r,g,b) tuples"""
    return [(palette[i], palette[i + 1], palette[i + 2]) for i in range(0, len(palette), 3)]


def rgb_palette_to_flat(palette: RGBList) -> list[int]:
    """Convert a palette of (r,g,b) tuples to a flat list that is usually used by Pillow images"""
    result = []
    for r, g, b in palette:
        result.append(r)
        result.append(g)
        result.append(b)
    return result


def flat_palette_to_vera(palette: list[int]) -> bytearray:
    """
    Convert a flat palette list usually obtained from Pillow images, to GB0R words (RGB in little-endian), suitable for Vera palette registers.
    The palette must be in 12 bit color space already! Because this routine just takes the upper 4 bits of every channel value.
    """
    return rgb_palette_to_vera(flat_palette_to_rgb(palette))


def rgb_palette_to_vera(palette_rgb: RGBList) -> bytearray:
    """
    Convert a palette in (r,g,b) format to GB0R words (RGB in little-endian), suitable for Vera palette registers.
    The palette must be in 12 bit color space already! Because this routine just takes the upper 4 bits of every channel value.
    """
    data = bytearray()
    for r, g, b in palette_rgb:
        r = r >> 4
        g = g >> 4
        b = b >> 4
        data.append(g << 4 | b)
        data.append(r)
    return data