48 lines
2 KiB
Python
48 lines
2 KiB
Python
"""Atari GR.9 (GTIA): 80x192, 16 luminance shades of one hue.
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Excellent greyscale (hue 0) or tinted monochrome (any of 16 hues) -- 16 real
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shades, not just dithered. ``base_color`` selects the hue (0..15); None = grey.
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"""
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from __future__ import annotations
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import numpy as np
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from ...convert.base import Conversion, perceptual_error
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from .. import palette as apal
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from . import _common
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WIDTH, HEIGHT = 80, 192
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PIXEL_ASPECT = 4.0
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def convert(img_rgb, palette_name="ntsc", dither_mode="floyd",
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intensive=False, base_color=None):
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hue = 0 if base_color is None else (int(base_color) & 0x0F)
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plab = apal.palette_lab(palette_name)
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prgb = apal.get_palette(palette_name).astype(np.uint8)
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img_mono, plab_mono = _common.luminance_lab(img_rgb, plab)
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ramp = apal.hue_ramp(hue) # 16 register values of this hue
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idx = _common.quantize_global(img_mono, plab_mono, ramp, dither_mode)
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val = (idx & 0x0F).astype(np.uint8) # GR.9 pixel = 4-bit luminance
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# GTIA mode 9 takes the hue from COLBK and the luminance from each pixel. A
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# COLBK of exactly $00, though, blanks the whole playfield to black -- the
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# register must be non-zero to enable the display. For a tinted hue that is
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# automatic ((hue<<4) != 0); for greyscale (hue 0) force a non-zero luminance
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# nibble, which the mode ignores for output (luminance still comes from the
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# pixels) but which switches the 16-shade display on.
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colbk = (hue & 0x0F) << 4
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if colbk == 0:
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colbk = 0x0E
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data = _common.split_screen(_common.pack_4bpp(val)) + bytes([colbk])
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preview = np.repeat(prgb[idx], int(PIXEL_ASPECT), axis=1)
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return Conversion(
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mode="gr9", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
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index_image=idx.astype(np.uint16), data=data, data_addr=_common.DATA_ADDR,
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viewer="gr9", preview_rgb=preview,
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error=perceptual_error(idx, img_mono, plab_mono),
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meta={"palette": palette_name, "dither": dither_mode, "hue": hue},
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)
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