140 lines
5.2 KiB
Python
140 lines
5.2 KiB
Python
"""Representation of Apple II screen memory."""
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import math
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import numpy as np
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import palette as palette_py
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class DHGRScreen:
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X_RES = 560
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Y_RES = 192
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def __init__(self, palette: palette_py.Palette):
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self.main = np.zeros(8192, dtype=np.uint8)
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self.aux = np.zeros(8192, dtype=np.uint8)
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self.palette = palette
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@staticmethod
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def y_to_base_addr(y: int) -> int:
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"""Maps y coordinate to screen memory base address."""
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a = y // 64
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d = y - 64 * a
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b = d // 8
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c = d - 8 * b
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return 1024 * c + 128 * b + 40 * a
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def pack(self, bitmap: np.ndarray):
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"""Packs an image into memory format (8k AUX + 8K MAIN)."""
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# The DHGR display encodes 7 pixels across interleaved 4-byte sequences
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# of AUX and MAIN memory, as follows:
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# PBBBAAAA PDDCCCCB PFEEEEDD PGGGGFFF
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# Aux N Main N Aux N+1 Main N+1 (N even)
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main_col = np.zeros(
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(self.Y_RES, self.X_RES // 14), dtype=np.uint8)
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aux_col = np.zeros(
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(self.Y_RES, self.X_RES // 14), dtype=np.uint8)
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for byte_offset in range(80):
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column = np.zeros(self.Y_RES, dtype=np.uint8)
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for bit in range(7):
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column |= (bitmap[:, 7 * byte_offset + bit].astype(
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np.uint8) << bit)
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if byte_offset % 2 == 0:
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aux_col[:, byte_offset // 2] = column
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else:
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main_col[:, (byte_offset - 1) // 2] = column
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for y in range(self.Y_RES):
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addr = self.y_to_base_addr(y)
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self.aux[addr:addr + 40] = aux_col[y, :]
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self.main[addr:addr + 40] = main_col[y, :]
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return
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def bitmap_to_image_rgb(self, bitmap: np.ndarray) -> np.ndarray:
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"""Convert our 2-bit bitmap image into a RGB image.
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Colour at every pixel is determined by the value of an n-bit sliding
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window and x % 4, which give the index into our RGB palette.
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"""
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image_rgb = np.empty((self.Y_RES, self.X_RES, 3), dtype=np.uint8)
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for y in range(self.Y_RES):
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bitmap_window = [False] * self.palette.PALETTE_DEPTH
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for x in range(self.X_RES):
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# Maintain a sliding window of pixels of width PALETTE_DEPTH
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bitmap_window = bitmap_window[1:] + [bitmap[y, x]]
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image_rgb[y, x, :] = self.palette.RGB[
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self.palette.bitmap_to_idx(
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np.array(bitmap_window, dtype=bool)), x % 4]
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return image_rgb
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@staticmethod
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def _sin(pos, phase0=0):
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x = pos % 12 + phase0
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return np.sin(x * 2 * np.pi / 12)
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@staticmethod
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def _cos(pos, phase0=0):
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x = pos % 12 + phase0
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return np.cos(x * 2 * np.pi / 12)
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def _read(self, line, pos):
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if pos < 0:
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return 0
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return 1 if line[pos] else 0
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def bitmap_to_image_ntsc(self, bitmap: np.ndarray) -> np.ndarray:
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y_width = 12
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u_width = 24
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v_width = 24
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contrast = 1
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# TODO: This is necessary to match OpenEmulator. I think it is because
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# they introduce an extra (unexplained) factor of 2 when applying the
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# Chebyshev/Lanczos filtering to the u and v components.
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saturation = 2
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# TODO: this phase shift is necessary to match OpenEmulator. I'm not
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# sure where it comes from - e.g. it doesn't match the phaseInfo
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# calculation for the signal phase at the start of the visible region.
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hue = 0.2 * (2 * np.pi)
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# Apply effect of saturation
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yuv_to_rgb = np.array(
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((1, 0, 0), (0, saturation, 0), (0, 0, saturation)), dtype=np.float)
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# Apply hue phase rotation
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yuv_to_rgb = np.matmul(np.array(
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((1, 0, 0), (0, np.cos(hue), np.sin(hue)), (0, -np.sin(hue),
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np.cos(hue)))),
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yuv_to_rgb)
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# Y'UV to R'G'B' conversion
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yuv_to_rgb = np.matmul(np.array(
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((1, 0, 1.139883), (1, -0.394642, -.5806227), (1, 2.032062, 0))),
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yuv_to_rgb)
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# Apply effect of contrast
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yuv_to_rgb *= contrast
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out_rgb = np.empty((bitmap.shape[0], bitmap.shape[1] * 3, 3),
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dtype=np.uint8)
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for y in range(bitmap.shape[0]):
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ysum = 0
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usum = 0
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vsum = 0
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line = np.repeat(bitmap[y], 3)
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for x in range(bitmap.shape[1] * 3):
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ysum += self._read(line, x) - self._read(line, x - y_width)
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usum += self._read(line, x) * self._sin(x) - self._read(
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line, x - u_width) * self._sin((x - u_width))
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vsum += self._read(line, x) * self._cos(x) - self._read(
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line, x - v_width) * self._cos((x - v_width))
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rgb = np.matmul(
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yuv_to_rgb, np.array(
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(ysum / y_width, usum / u_width,
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vsum / v_width)).reshape((3, 1))).reshape(3)
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r = min(255, max(0, rgb[0] * 255))
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g = min(255, max(0, rgb[1] * 255))
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b = min(255, max(0, rgb[2] * 255))
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out_rgb[y, x, :] = (r, g, b)
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return out_rgb
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