toGamut() throws error "Cannot read properties of undefined (reading '1')" on other modes

[drwpow]

Problem

The signature of toGamut() allows a mode as the 2nd param, e.g. toGamut('rgb', 'lab'). But on other modes, a runtime error occurs:

  TypeError [Error]: Cannot read properties of undefined (reading '1')
      at /evercoder/culori/src/clamp.js:239:26
      at TestContext.<anonymous> (/evercoder/culori/test/clamp.test.js:184:34)
      at Test.runInAsyncScope (node:async_hooks:214:14)
      at Test.run (node:internal/test_runner/test:1062:25)
      at Test.processPendingSubtests (node:internal/test_runner/test:752:18)
      at Test.postRun (node:internal/test_runner/test:1191:19)
      at Test.run (node:internal/test_runner/test:1119:12)
      at async Test.processPendingSubtests (node:internal/test_runner/test:752:7)

Part of the problem is there are no tests for toGamut() utilizing the 2nd param. The line that throws is here:

    let epsilon = (ranges.c[1] - ranges.c[0]) / 4000; // 0.0001 for oklch()
                          ^
                          Cannot read properties of undefined 

ranges will be an object matching the mode, so anything without a c channel (OKLCH, LCH) will throw an error.

Reproduction

Test the following code out in clamp.test.js:

  assert.equal(
    formatCss(toGamut('rgb', 'lab')({ mode: 'lab', l: 0.97607, a: -15.753, b: 93.388, })),
    'color(srgb 0.4906 0.1387 0.159)',
    'Lab'
  );
  assert.equal(
    formatCss(toGamut('rgb', 'lch')({ mode: 'lch', l: 0.512345, c:21.2, h: 130 })),
    'color(srgb 0.41587, 0.503670, 0.36664)',
    'LCh'
  );

Expectation

Since toGamut() allows specifying a mode, I‘d either expect:

• All modes to work, or

• An error to be thrown if a mode is not valid

• I’m willing to open a PR

[danburzo]

The toGamut() method accepts only LCH-like spaces (having lightness and chroma components) for performing gamut mapping, and unfortunately the API docs don’t specify that. I think it’s fair to throw early if !ranges.l || !ranges.c:

culori/src/clamp.js

Line 207 in 2bedb8f

const { ranges } = getMode(mode);

I’ll happily accept a PR for this.

[drwpow]

That makes sense. And sure I could open a PR!

Scanning over Culori’s colorspaces it looked like all the ones with “c” and “h” components were all Chroma and Hue? (obviously LCH/Oklab but also including LCHuv, JCH, etc.). Are there any exceptions that likely wouldn’t work?

[danburzo]

Yes, there are a few assumptions scattered throughout the library that I’m not too thrilled about, and that l is lightness, c is chroma, and h is hue is one of them :-) I’ve added the error in the commit above.

[danburzo]

Available in culori@v4.0.2.