Apple-2-SW/ii-pix
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NTSC conversion should be using YIQ space instead of YUV, which seems

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to explain several fudge factors I needed to include to match colours.
This commit is contained in:
kris 2021-11-02 23:28:58 +00:00
parent df0adec8aa
commit bf76271d75
4 changed files with 928 additions and 927 deletions
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17
convert.py
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@ -84,14 +84,17 @@ def main():
screen, rgb, dither, args.lookahead, args.verbose, rgb_to_cam16)
# Show output image by rendering in target palette
output_palette = palette_py.PALETTES[args.show_palette or args.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)
# TODO: if output_palette_name == "ntsc" show bitmap_to_image_ntsc instead
output_rgb = output_screen.bitmap_to_image_rgb(bitmap)
out_image = Image.fromarray(image_py.linear_to_srgb(output_rgb).astype(
np.uint8))
out_image = image_py.resize(out_image, screen.X_RES, screen.Y_RES * 2,
srgb_output=True)
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, screen.Y_RES * 2,
srgb_output=True)
if args.show_output:
out_image.show()

3
ntsc_colours.py
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@ -19,8 +19,7 @@ def main():
# pixel, using NTSC emulation.
# Double Hi-Res has a timing shift that rotates the displayed bits one
# position with respect to NTSC phase.
# TODO: should be 3? Do I have a compensating off-by-one in bitmap_to_ntsc?
ntsc_shift = 2
ntsc_shift = 1
for j in range(ntsc_shift, ntsc_shift + 4):
bitmap = np.zeros((1, 11 + ntsc_shift), dtype=bool)
for bits in range(256):

1784
palette_ntsc.py
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File diff suppressed because it is too large Load Diff

51
screen.py
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@ -1,5 +1,6 @@
"""Representation of Apple II screen memory."""
import math
import numpy as np
import palette as palette_py
@ -84,51 +85,49 @@ class DHGRScreen:
def bitmap_to_image_ntsc(self, bitmap: np.ndarray) -> np.ndarray:
y_width = 12
u_width = 24
v_width = 24
i_width = 24
q_width = 24
contrast = 1
# TODO: where does this come from? OpenEmulator looks like it should
# use a value of 1.0 by default.
saturation = 2
# Fudge factor to make colours line up with OpenEmulator
# TODO: where does this come from - is it due to the band-pass
# filtering they do?
hue = -0.3
saturation = 1
# DHGR has a timing shift of 1/4 phase, i.e x=0 is actually 1/4 phase.
# XXX should use (x + 1) % 4 ?
hue = math.pi / 2
# Apply effect of saturation
yuv_to_rgb = np.array(
yiq_to_rgb = np.array(
((1, 0, 0), (0, saturation, 0), (0, 0, saturation)), dtype=np.float)
# Apply hue phase rotation
yuv_to_rgb = np.matmul(np.array(
yiq_to_rgb = np.matmul(np.array(
((1, 0, 0), (0, np.cos(hue), np.sin(hue)), (0, -np.sin(hue),
np.cos(hue)))),
yuv_to_rgb)
# Y'UV to R'G'B' conversion
yuv_to_rgb = np.matmul(np.array(
((1, 0, 1.13983), (1, -0.39465, -.58060), (1, 2.03211, 0))),
yuv_to_rgb)
yiq_to_rgb)
# Y'IQ to R'G'B' conversion
yiq_to_rgb = np.matmul(np.array(
((1, 0.956, 0.621), (1, -0.272, -.647), (1, -1.107, 1.704))),
yiq_to_rgb)
# Apply effect of contrast
yuv_to_rgb *= contrast
yiq_to_rgb *= contrast
out_rgb = np.empty((bitmap.shape[0], bitmap.shape[1] * 3, 3),
dtype=np.uint8)
for y in range(bitmap.shape[0]):
ysum = 0
usum = 0
vsum = 0
isum = 0
qsum = 0
line = np.repeat(bitmap[y], 3)
for x in range(bitmap.shape[1] * 3):
ysum += self._read(line, x) - self._read(line, x - y_width)
usum += self._read(line, x) * self._sin(x) - self._read(
line, x - u_width) * self._sin((x - u_width))
vsum += self._read(line, x) * self._cos(x) - self._read(
line, x - v_width) * self._cos((x - v_width))
isum += self._read(line, x) * self._sin(x) - self._read(
line, x - i_width) * self._sin((x - i_width))
qsum += self._read(line, x) * self._cos(x) - self._read(
line, x - q_width) * self._cos((x - q_width))
rgb = np.matmul(
yuv_to_rgb, np.array(
(ysum / y_width, usum / u_width,
vsum / v_width)).reshape((3, 1))).reshape(3)
yiq_to_rgb, np.array(
(ysum / y_width, isum / i_width,
qsum / q_width)).reshape((3, 1))).reshape(3)
r = min(255, max(0, rgb[0] * 255))
g = min(255, max(0, rgb[1] * 255))
b = min(255, max(0, rgb[2] * 255))