Show colorized items#1
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WalkthroughThe version number in the package configuration file was incremented. In the main module, two new functions for colorized terminal output were added, the hashing logic was refactored for better color distribution, and helper functions for ANSI color codes and contrast were introduced. The module's export list was updated accordingly. Changes
Sequence Diagram(s)sequenceDiagram
participant User
participant Data.Hashable.Color
User->>Data.Hashable.Color: rgbHash(a)
Data.Hashable.Color->>Data.Hashable.Color: _rgbHash(a)
Data.Hashable.Color-->>User: (r, g, b)
User->>Data.Hashable.Color: rgbHashBgShow(a)
Data.Hashable.Color->>Data.Hashable.Color: _rgbHash(a)
Data.Hashable.Color->>Data.Hashable.Color: _altColor(r, g, b)
Data.Hashable.Color->>Data.Hashable.Color: _ansiSeqBg(r, g, b), _ansiSeqFg(alt)
Data.Hashable.Color-->>User: Colored string with background and contrasting foreground
User->>Data.Hashable.Color: rgbHashFgShow(a)
Data.Hashable.Color->>Data.Hashable.Color: _rgbHash(a)
Data.Hashable.Color->>Data.Hashable.Color: _altColor(r, g, b)
Data.Hashable.Color->>Data.Hashable.Color: _ansiSeqFg(r, g, b), _ansiSeqBg(alt)
Data.Hashable.Color-->>User: Colored string with foreground and contrasting background
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🔇 Additional comments (6)
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Actionable comments posted: 1
🧹 Nitpick comments (3)
src/Data/Hashable/Color.hs (3)
36-37: Add documentation for the hash mixing function.The implementation looks correct for hash mixing, but consider adding a comment explaining the purpose of the scrambling and the choice of the mixing constant.
+-- | Mix bits of a hash value for better color distribution _scramble :: Int -> Int _scramble x = ((shiftR x 16) `xor` x) * 0x45d9f3b
39-45: Consider if double scrambling is necessary.The implementation correctly extracts RGB components, but applying
_scrambletwice might be overkill. Consider testing if single scrambling provides sufficient color distribution.If single scrambling proves sufficient:
- h = _scramble (_scramble (hash x)) + h = _scramble (hash x)
72-83: LGTM! Well-implemented colorized background function.The function correctly applies ANSI codes and resets terminal state. Consider adding a usage example in the documentation.
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colorhash.cabal(1 hunks)src/Data/Hashable/Color.hs(2 hunks)
🔇 Additional comments (6)
colorhash.cabal (1)
4-4: LGTM! Appropriate version bump for new functionality.The minor version increment correctly reflects the addition of new public functions while maintaining backward compatibility.
src/Data/Hashable/Color.hs (5)
15-23: LGTM! Clean module structure with well-organized exports.The module exports are logically grouped and the new functions are appropriately categorized under "Show items with color".
25-31: LGTM! Appropriate imports and clean type alias.The
Data.Bitsimport is necessary for the hash scrambling operations, and theCol8type alias improves code readability.
47-54: LGTM! Correct ANSI escape sequence implementation.The 24-bit color ANSI codes are properly formatted and the function composition approach is clean and efficient.
68-70: LGTM! Good refactoring for code reuse.Using the shared
_rgbHashhelper improves consistency and maintainability.
84-94: LGTM! Well-implemented colorized foreground function.The function correctly applies ANSI codes and resets terminal state. The symmetric design with
rgbHashBgShowis clean and intuitive.
| _altColor :: Col8 -> Col8 | ||
| _altColor ~(r, g, b) | ||
| | 1063 * fromEnum r + 3576 * fromEnum g + 361 * fromEnum b <= 200000 = (255, 255, 255) | ||
| | otherwise = (0, 0, 0) |
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💡 Verification agent
🧩 Analysis chain
Verify the luminance calculation weights.
The contrast calculation uses non-standard luminance weights. Consider using ITU-R BT.709 standard weights for more accurate perceptual luminance.
The current weights (1063, 3576, 361) don't match standard RGB-to-luminance coefficients. Standard weights are approximately (2990, 5870, 1140) when scaled to avoid floating-point arithmetic. Please verify if these custom weights are intentional or if they should be updated to standard values.
🌐 Web query:
What are the standard ITU-R BT.709 RGB to luminance conversion coefficients?
💡 Result:
ITU-R BT.709 defines specific coefficients for converting RGB values to luminance (Y'). According to the standard, the RGB to luminance conversion coefficients are:
- Red (R): 0.2126
- Green (G): 0.7152
- Blue (B): 0.0722[4][7][8]
These coefficients are used in the following formula to derive the luminance signal:
Y' = 0.2126 × R' + 0.7152 × G' + 0.0722 × B'[4][5]
Where R', G', and B' represent the gamma-corrected (non-linear) RGB values.
The BT.709 coefficients differ from those used in other standards like Rec.601/BT.601, which uses 0.299 for red, 0.587 for green, and 0.114 for blue[7]. This difference is significant because the BT.709 coefficients are designed to match the primaries and white points of HDTV systems, allowing luma to correspond more closely to actual luminance[8].
For the constant luminance version (YC') specified in BT.2020, slightly different coefficients are used:
- Red: 0.2627
- Green: 0.6780
- Blue: 0.0593[5]
The BT.709 standard is primarily used for HDTV applications and has become the basis for many modern video formats and color space conversions.
Citations:
- 1: https://en.wikipedia.org/wiki/Rec._709
- 2: https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2407-2017-PDF-E.pdf
- 3: https://glenwing.github.io/docs/ITU-R-BT.709-1.pdf
- 4: https://en.wikipedia.org/wiki/YCbCr
- 5: https://www.synopsys.com/blogs/chip-design/color-space-conversions-display.html
- 6: https://www.color.org/chardata/rgb/BT709.xalter
- 7: http://avisynth.nl/index.php/Colorimetry
- 8: https://www.scribd.com/document/550460791/Rec-709
- 9: Conversion between RGB and YCbCr may be wrong JuliaGraphics/Colors.jl#453
- 10: https://avisynthplus.readthedocs.io/en/latest/avisynthdoc/advancedtopics/colorimetry.html
Use ITU-R BT.709 Luminance Weights for Contrast
The _altColor function currently applies custom weights (1063, 3576, 361) which don’t align with BT.709’s perceptual luminance coefficients. Update to the standard values and adjust the threshold accordingly.
• File: src/Data/Hashable/Color.hs
Lines: 56–59
Suggested diff:
-altColor :: Col8 -> Col8
-_altColor ~(r, g, b)
- | 1063 * fromEnum r + 3576 * fromEnum g + 361 * fromEnum b <= 200000 = (255, 255, 255)
- | otherwise = (0, 0, 0)
+_altColor :: Col8 -> Col8
+_altColor ~(r, g, b)
+ -- BT.709 Y' = 0.2126R + 0.7152G + 0.0722B (scaled to integers)
+ | 2126 * fromEnum r + 7152 * fromEnum g + 722 * fromEnum b <= 400000 = (255, 255, 255)
+ | otherwise = (0, 0, 0)• New threshold 400000 preserves the original 15.7% luminance cutoff (200 000/1 275 000 ≈ 0.157 → 0.157×2 550 000 ≈ 400 000).
This ensures more accurate, standard-compliant contrast decisions.
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| _altColor :: Col8 -> Col8 | |
| _altColor ~(r, g, b) | |
| | 1063 * fromEnum r + 3576 * fromEnum g + 361 * fromEnum b <= 200000 = (255, 255, 255) | |
| | otherwise = (0, 0, 0) | |
| _altColor :: Col8 -> Col8 | |
| _altColor ~(r, g, b) | |
| -- BT.709 Y' = 0.2126R + 0.7152G + 0.0722B (scaled to integers) | |
| | 2126 * fromEnum r + 7152 * fromEnum g + 722 * fromEnum b <= 400000 = (255, 255, 255) | |
| | otherwise = (0, 0, 0) |
🤖 Prompt for AI Agents
In src/Data/Hashable/Color.hs around lines 56 to 59, the _altColor function uses
non-standard luminance weights (1063, 3576, 361) for contrast calculation.
Replace these with the ITU-R BT.709 standard weights scaled appropriately (2990
for red, 5870 for green, and 1140 for blue) and update the luminance threshold
to 400000 to maintain the original contrast cutoff. This change aligns the
luminance calculation with perceptual standards for better accuracy.
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