fix geom, add unittest

src/groovylight/gamma.py

@@ -0,0 +1,52 @@
+# Gamma correction by adjusting the display OE/Expose timings.
+
+
+# Most gamma correction is done on the values being displayed.
+# i.e gammacorrect (RGB) -> RGB (adjusted). However this adds
+# a complex look-up step which adds complexity and cycles.
+# There is a simpler solution which uses some properties of the
+# gamma function as well as the fact that we are manually doing
+# color depth using BCM/PWM.
+#
+# Consider the default BCM timing layout:
+# MSB  MSB-1  MSB-2  MSB-3
+# P*8    P*4    P*2   P
+# that is, we have a baseline display, measured in clocks/us/whatever
+# and then the next most significant bit is displayed for twice that,
+# four times that, and so on.
+# But, we can adjust the individual bit timings to adjust the brightness
+# curve as we see fit. This has numerous advantages:
+# 1. It's free, we don't have to do any math on the board, just adjusting
+#    an existing process.
+# 2. We can go more granular that n-bits of color. This means that the gamma
+#    curve will be effective and accurate regardless of the color depth.
+#
+# This file contains code to generate these timing adjustments and 
+# control/quantify them.
+
+from math import pow
+
+
+
+def _gammavec(vals: [float], g: float) -> [float]:
+    return [pow(x,g) for x in vals]
+
+def _nbit_scale(f, nbits:int) -> [float]:
+    """Computes the equivalent linear value for each bit of n_bits.
+    That is, the list contains scalar values that are doubling as they progress,
+    [ x, 2x, 4x ] such that the sum(list) = 7x = f
+    """
+    base = float(f) / (pow(2.0, nbits) - 1.0)
+    return [base * pow(2.0, x) for x in range(nbits)]
+
+
+def gamma_timings(gamma:float = 2.2, nbits:int = 8, max_clocks: int = 4096):
+    """Computes the clock cycle timings for a given gamma correction.
+    """
+    linear_values = _nbit_scale(1.0, nbits)
+    gamma_values = _gammavec(linear_values, gamma)
+
+    bclk_ratio = max_clocks / gamma_values[-1]
+    result = [round(bclk_ratio * x) for x in gamma_values]
+    return result
+

src/groovylight/geom.py

@@ -3,9 +3,11 @@
 
 from enum import Enum
 from dataclasses import dataclass
+from typing import Self
+from math import ceil, log2
 
 
-@dataclass(frozen=True, order=True)
+@dataclass(frozen=True)
 class Coord:
     """Coordinate class. Uses computer-graphics standard coordinate system,
     where X=0, Y=0 is top left. +X goes right. +Y goes down.
@@ -13,11 +15,29 @@ class Coord:
 
     x: int
     y: int
-    
+
     def __post_init__(self):
         if self.x < 0 or self.y < 0:
             raise RuntimeError("x and y must both be >= 0")
 
+    def __lt__(self, other):
+        return self.x < other.x and self.y < other.y
+
+    def __gt__(self, other):
+        return self.x > other.x and self.y > other.y
+
+    def __eq__(self, other):
+        return self.x == other.x and self.y == other.y
+
+    def __neq__(self, other):
+        return not (self.x == other.x and self.y == other.y)
+
+    def __le__(self, other):
+        return self.x <= other.x and self.y <= other.y
+
+    def __ge__(self, other):
+        return self.x >= other.x and self.y >= other.y
+
 
 @dataclass(frozen=True)
 class BBox:
@@ -32,7 +52,27 @@ class BBox:
             raise RuntimeError("topleft must be strictly less than bottomright")
 
     def contains(self, c: Coord) -> bool:
-        return c > self.topleft and c < self.bottomright
+        return c >= self.topleft and c <= self.bottomright
+
+    @property
+    def width(self) -> int:
+        return self.bottomright.x - self.topleft.x
+
+    @property
+    def height(self) -> int:
+        return self.bottomright.y - self.topleft.y
+
+    def intersects(self, other: Self) -> bool:
+        ## other leftmost edge is right of our rightmost edge
+        x1 = other.topleft.x > self.bottomright.x
+        # our leftmost edge is to the right of other rightmost edge
+        x2 = self.topleft.x > other.bottomright.x
+        # other top edge is below (greater than!) our bottom edge
+        y1 = other.topleft.y > self.bottomright.y
+        # our top edge is below other bottom edge.
+        y2 = self.topleft.y > other.bottomright.y
+
+        return not (x1 or x2 or y1 or y2)
 
 
 @dataclass(frozen=True)
@@ -44,6 +84,10 @@ class DisplayDimensions:
 
     length: int
     height: int
+    mux: int = 2  # number of lines driven at once.
+
+    def addr_bits(self) -> int:
+        return ceil(log2(self.height / self.mux))
 
 
 class DisplayRotation(Enum):
@@ -68,7 +112,7 @@ class DisplayRotation(Enum):
 
 
 @dataclass(frozen=True)
-class _DisplayString:
+class DisplayString:
     """Internal class to represent a string of HUB75 displays.
 
     position: (X,Y) coordinates of the local top-left of the display
@@ -81,6 +125,7 @@ class _DisplayString:
     position: Coord
     dimensions: DisplayDimensions
     rotation: DisplayRotation
+    # TODO: encode muxing
 
     @property
     def bbox(self) -> BBox:
@@ -103,10 +148,13 @@ class _DisplayString:
         """Checks if the given coordinate is inside this display."""
         return self.bbox.contains(coord)
 
+    def intersects(self, box: BBox) -> bool:
+        """Checks if the given BBox intersects with this display"""
+        return self.bbox.intersects(box)
+
 
 class DisplayGeometry:
-    """Represents a display based on several strings in different positions.
-    """
+    """Represents a display based on several strings in different positions."""
 
     def __init__(self, *, strict: bool = False):
         self.strict = strict

src/groovylight/tests/test_geom.py

@@ -0,0 +1,32 @@
+from ..geom import Coord, BBox
+
+import pytest
+
+def test_coord_comparison():
+    c1 = Coord(0,0)
+    c2 = Coord(0,1)
+    c3 = Coord(1,1)
+    c3_other = Coord(1,1)
+
+    assert c1 < c3
+    assert not c1 < c2, "both x,y must be greater/lt/eq"
+    assert c2 <= c3
+
+    assert c3 == c3_other, "Coords with same numbers should equal each other"
+    assert c3 != c2
+
+def test_coord_construction():
+    with pytest.raises(RuntimeError):
+        Coord(0,-1)
+
+
+def test_bbox():
+    b = BBox(Coord(1,1), Coord(3,2))
+
+    assert b.width == 2
+    assert b.height == 1
+
+    assert b.contains(Coord(1,2))
+    assert not b.contains(Coord(0,0))
+    
+    # TODO: test .intersect(other)

src/groovylight/tests/test_hub75.py

@@ -5,7 +5,7 @@ from amaranth.lib.wiring import In, Out
 from amaranth.lib.memory import Memory, WritePort
 from amaranth.sim import Simulator
 
-from .bitslicer import Hub75StringDriver, Rgb666Layout
+from ..bitslicer import Hub75StringDriver, Rgb666Layout
 
 
 def test_stringdriver():

src/groovylight/tests/test_swapbuffer.py

@@ -5,7 +5,7 @@ from amaranth.lib.wiring import In, Out
 from amaranth.lib.memory import Memory, WritePort
 from amaranth.sim import Simulator
 
-from .bitslicer import Hub75StringDriver, Rgb666Layout, SwapBuffer
+from ..bitslicer import Hub75StringDriver, Rgb666Layout, SwapBuffer
 
 
 def test_swapbuffer():