ii-pix/palette.py

"""RGB colour palettes to target for Apple II image conversions."""

import colour
import numpy as np
import image
import palette_ntsc


class Palette:
    SRGB = None
    RGB = {}
    CAM16UCS = {}

    # How many successive screen pixels are used to compute output pixel 
    # palette index.
    PALETTE_DEPTH = None

    def __init__(self):
        self.RGB = {}
        # XXX RGB and CAM16UCS should be indexed by (pixels_nbit, phase)
        for k, v in self.SRGB.items():
            self.RGB[k] = (np.clip(image.srgb_to_linear_array(v / 255), 0.0,
                                   1.0) * 255).astype(np.uint8)
            with colour.utilities.suppress_warnings(colour_usage_warnings=True):
                self.CAM16UCS[k] = colour.convert(
                    v / 255, "sRGB", "CAM16UCS").astype(np.float32)

    def _pixel_phase_shifts(self, phase_0_rgb):
        rgb_phases = {}
        for pixels, rgb in phase_0_rgb.items():
            rgb_phases[pixels, 0] = rgb
            for phase in range(1, 4):
                msb = pixels & (1 << (self.PALETTE_DEPTH - 1))
                pixels <<= 1 | (msb >> (self.PALETTE_DEPTH - 1))
                rgb_phases[pixels, phase] = rgb
        return rgb_phases

    def bitmap_to_idx(self, pixels: np.array) -> int:
        """Converts a bitmap of pixels into integer representation.

        Args:
            pixels: 1-D array of booleans, representing a window of pixels from
              L to R.  Must be of size <= 8

        Returns:
            8-bit integer representation of pixels, suitable for use as an
            index into palette arrays
        """
        return np.packbits(
            # numpy uses big-endian representation which is the opposite
            # order to screen representation (i.e. LSB is the left-most
            # screen pixel), so we need to flip the order
            np.flip(pixels, axis=0)
        )[0]


class ToHgrPalette(Palette):
    """4-bit palette used as default by other DHGR image converters."""
    PALETTE_DEPTH = 4

    # Default tohgr/bmp2dhr palette
    SRGB = {
        0: np.array((0, 0, 0)),  # Black
        8: np.array((148, 12, 125)),  # Magenta
        4: np.array((99, 77, 0)),  # Brown
        12: np.array((249, 86, 29)),  # Orange
        2: np.array((51, 111, 0)),  # Dark green
        10: np.array((126, 126, 126)),  # Grey2
        6: np.array((67, 200, 0)),  # Green
        14: np.array((221, 206, 23)),  # Yellow
        1: np.array((32, 54, 212)),  # Dark blue
        9: np.array((188, 55, 255)),  # Violet
        5: np.array((126, 126, 126)),  # Grey1
        13: np.array((255, 129, 236)),  # Pink
        3: np.array((7, 168, 225)),  # Med blue
        11: np.array((158, 172, 255)),  # Light blue
        7: np.array((93, 248, 133)),  # Aqua
        15: np.array((255, 255, 255)),  # White
    }


class OpenEmulatorPalette(Palette):
    """4-bit palette chosen to approximately match OpenEmulator output."""
    PALETTE_DEPTH = 4

    # OpenEmulator
    SRGB = {
        0: np.array((0, 0, 0)),  # Black
        8: np.array((203, 0, 121)),  # Magenta
        4: np.array((99, 103, 0)),  # Brown
        12: np.array((244, 78, 0)),  # Orange
        2: np.array((0, 150, 0)),  # Dark green
        10: np.array((130, 130, 130)),  # Grey2
        6: np.array((0, 235, 0)),  # Green
        14: np.array((214, 218, 0)),  # Yellow
        1: np.array((20, 0, 246)),  # Dark blue
        9: np.array((230, 0, 244)),  # Violet
        5: np.array((130, 130, 130)),  # Grey1
        13: np.array((244, 105, 235)),  # Pink
        3: np.array((0, 174, 243)),  # Med blue
        11: np.array((160, 156, 244)),  # Light blue
        7: np.array((25, 243, 136)),  # Aqua
        15: np.array((244, 247, 244)),  # White
    }


class VirtualIIPalette(Palette):
    """4-bit palette exactly matching Virtual II emulator output."""
    PALETTE_DEPTH = 4

    SRGB = {
        0: np.array((0, 0, 0)),  # Black
        8: np.array((231, 36, 66)),  # Magenta
        4: np.array((154, 104, 0)),  # Brown
        12: np.array((255, 124, 0)),  # Orange
        2: np.array((0, 135, 45)),  # Dark green
        10: np.array((104, 104, 104)),  # Grey2
        6: np.array((0, 222, 0)),  # Green
        14: np.array((255, 252, 0)),  # Yellow
        1: np.array((1, 30, 169)),  # Dark blue
        9: np.array((230, 73, 228)),  # Violet
        5: np.array((185, 185, 185)),  # Grey1
        13: np.array((255, 171, 153)),  # Pink
        3: np.array((47, 69, 255)),  # Med blue
        11: np.array((120, 187, 255)),  # Light blue
        7: np.array((83, 250, 208)),  # Aqua
        15: np.array((255, 255, 255)),  # White
    }


class NTSCPalette(Palette):
    """8-bit NTSC palette computed by averaging chroma signal over 8 pixels."""
    PALETTE_DEPTH = 8

    # Computed using ntsc_colours.py
    SRGB = palette_ntsc.SRGB


PALETTES = {
    'openemulator': OpenEmulatorPalette,
    'virtualii': VirtualIIPalette,
    'tohgr': ToHgrPalette,
    'ntsc': NTSCPalette
}

DEFAULT_PALETTE = 'ntsc'