Merge pull request #35 from treeform/guzba

0.2.6, rounding + test rgba->rgbx, rgbx->rgba

chroma.nimble

@@ -1,10 +1,8 @@
-# Package
-version = "0.2.5"
+version = "0.2.6"
 author = "Andre von Houck"
 description = "Everything you want to do with colors"
 license = "MIT"
 
 srcDir = "src"
 
-# Deps
 requires "nim >= 1.0.0"

src/chroma.nim

@@ -3,7 +3,7 @@
 ##
 
 import chroma/colortypes, chroma/distance, chroma/names, chroma/temperature,
-    chroma/transformations, hashes, strutils, tables
+    chroma/transformations, std/hashes, std/math, std/strutils, std/tables
 
 export colortypes, distance, temperature, transformations
 
@@ -197,9 +197,9 @@ proc toHtmlRgb*(c: Color): string =
   ## * blue -> rgb(0,0,255)
   ## * white -> rgb(255,255,255)
   "rgb(" &
-    $int(c.r * 255) & ", " &
-    $int(c.g * 255) & ", " &
-    $int(c.b * 255) &
+    $round(c.r * 255).int & ", " &
+    $round(c.g * 255).int & ", " &
+    $round(c.b * 255).int &
   ")"
 
 proc parseHtmlRgba*(text: string): Color =
@@ -230,9 +230,9 @@ proc toHtmlRgba*(c: Color): string =
   ## * blue -> rgb(0,0,255)
   ## * white -> rgb(255,255,255)
   "rgba(" &
-    $int(c.r * 255) & ", " &
-    $int(c.g * 255) & ", " &
-    $int(c.b * 255) & ", " &
+    $round(c.r * 255).int & ", " &
+    $round(c.g * 255).int & ", " &
+    $round(c.b * 255).int & ", " &
     $c.a &
   ")"
 
@@ -336,16 +336,16 @@ proc mixCMYK*(colorA, colorB: Color): Color =
 
 proc mix*(a, b: ColorRGB): ColorRGB =
   ## Mixes two ColorRGB colors together using simple average.
-  result.r = a.r div 2 + b.r div 2
-  result.g = a.g div 2 + b.g div 2
-  result.b = a.b div 2 + b.b div 2
+  result.r = ((a.r.uint32 + b.r) div 2).uint8
+  result.g = ((a.g.uint32 + b.g) div 2).uint8
+  result.b = ((a.b.uint32 + b.b) div 2).uint8
 
 proc mix*(a, b: ColorRGBA): ColorRGBA =
   ## Mixes two ColorRGBA colors together using simple average.
-  result.r = a.r div 2 + b.r div 2
-  result.g = a.g div 2 + b.g div 2
-  result.b = a.b div 2 + b.b div 2
-  result.a = a.a div 2 + b.a div 2
+  result.r = ((a.r.uint32 + b.r) div 2).uint8
+  result.g = ((a.g.uint32 + b.g) div 2).uint8
+  result.b = ((a.b.uint32 + b.b) div 2).uint8
+  result.a = ((a.a.uint32 + b.a) div 2).uint8
 
 func distance*(c1, c2: SomeColor): float32 =
   ## A distance function based on CIEDE2000 color difference formula

src/chroma/transformations.nim

@@ -12,7 +12,7 @@
 ## and link to a mirror of the C file:
 ## - https://github.com/cran/colorspace/blob/master/src/colorspace.c
 
-import colortypes, math
+import colortypes, std/math
 
 proc rgba*(c: ColorRGBX): ColorRGBA {.inline.} =
   ## Convert a premultiplied alpha RGBA to a straight alpha RGBA.
@@ -21,16 +21,16 @@ proc rgba*(c: ColorRGBX): ColorRGBA {.inline.} =
   result.b = c.b
   result.a = c.a
   if result.a != 0 and result.a != 255:
-    let multiplier = ((255 / c.a.float32) * 255).uint32
-    result.r = ((result.r.uint32 * multiplier) div 255).uint8
-    result.g = ((result.g.uint32 * multiplier) div 255).uint8
-    result.b = ((result.b.uint32 * multiplier) div 255).uint8
+    let multiplier = round((255 / c.a.float32) * 255).uint32
+    result.r = ((result.r.uint32 * multiplier + 127) div 255).uint8
+    result.g = ((result.g.uint32 * multiplier + 127) div 255).uint8
+    result.b = ((result.b.uint32 * multiplier + 127) div 255).uint8
 
 proc rgbx*(c: ColorRGBA): ColorRGBX {.inline.} =
   ## Convert a straight alpha RGBA to a premultiplied alpha RGBA.
-  result.r = ((c.r.uint32 * c.a.uint32) div 255).uint8
-  result.g = ((c.g.uint32 * c.a.uint32) div 255).uint8
-  result.b = ((c.b.uint32 * c.a.uint32) div 255).uint8
+  result.r = ((c.r.uint32 * c.a.uint32 + 127) div 255).uint8
+  result.g = ((c.g.uint32 * c.a.uint32 + 127) div 255).uint8
+  result.b = ((c.b.uint32 * c.a.uint32 + 127) div 255).uint8
   result.a = c.a
 
 proc rgbx*(c: ColorRGB): ColorRGBX {.inline.} =
@@ -42,9 +42,9 @@ proc rgbx*(c: ColorRGB): ColorRGBX {.inline.} =
 
 proc rgb*(c: Color): ColorRGB {.inline.} =
   ## Convert Color to ColorRGB
-  result.r = uint8(c.r * 255)
-  result.g = uint8(c.g * 255)
-  result.b = uint8(c.b * 255)
+  result.r = round(c.r * 255).uint8
+  result.g = round(c.g * 255).uint8
+  result.b = round(c.b * 255).uint8
 
 proc color*(c: ColorRGB): Color {.inline.} =
   ## Convert ColorRGB to Color
@@ -55,10 +55,10 @@ proc color*(c: ColorRGB): Color {.inline.} =
 
 proc rgba*(c: Color): ColorRGBA {.inline.} =
   ## Convert Color to ColorRGBA
-  result.r = uint8(c.r * 255)
-  result.g = uint8(c.g * 255)
-  result.b = uint8(c.b * 255)
-  result.a = uint8(c.a * 255)
+  result.r = round(c.r * 255).uint8
+  result.g = round(c.g * 255).uint8
+  result.b = round(c.b * 255).uint8
+  result.a = round(c.a * 255).uint8
 
 proc color*(c: ColorRGBA): Color {.inline.} =
   ## Convert ColorRGBA to Color

tests/test_colors.nim

@@ -1,4 +1,4 @@
-import chroma, chroma/transformations, macros, sequtils, strutils, unittest
+import chroma, chroma/transformations, std/macros, std/sequtils, std/strutils, std/unittest, std/math
 
 when not defined(js):
   import parsecsv
@@ -397,6 +397,30 @@ suite "temperature":
     doAssert fromTemperature(6500).almostEqual(color(1.0, 0.9753435850143433, 0.9935365319252014, 1.0))  # LCD or CRT screen
     doAssert fromTemperature(15000).almostEqual(color(0.7009154558181763, 0.7981580495834351, 1.0, 1.0))  # Clear blue poleward sky
 
+suite "premultiplied alpha":
+  test "rgba -> rgbx":
+    for a in 0.uint8 .. 255:
+      for r in 0.uint8 .. 255:
+        doAssert rgba(r, 0, 0, a).rgbx == rgbx(
+          round(r.float32 * a.float32 / 255).uint8,
+          0,
+          0,
+          a
+        )
+
+  test "rgbx -> rgba":
+    for a in 0.uint8 .. 255:
+      for r in 0.uint8 .. 255:
+        let
+          rgbx = rgba(r, 0, 0, a).rgbx
+          multiplier = round((255 / rgbx.a.float32) * 255).uint32
+        doAssert rgbx.rgba == rgba(
+          ((rgbx.r * multiplier + 127) div 255).uint8,
+          0,
+          0,
+          rgbx.a.uint8
+        )
+
 when false:
   # example in readme:
   import chroma