Added resolution unit option in tiff method

[ompal-sisodiya]

• Added resolution unit in option.param while using tiff method
• Added required test cases

[lovell]

Thank you Ompal for the PR, looks good. Please can you add a unit test that verifies the EXIF metadata in the output has the expected resolution unit based on this new option.

[lovell]

Sorry, I should have been clearer, I was thinking of a unit test that verifies the EXIF metadata of the output image (rather than just inspecting internal options), perhaps using an approach similar to the existing metadata tests:

sharp/test/unit/metadata.js

Lines 53 to 56 in 1ff84b2

	const exif = exifReader(metadata.exif);
	assert.strictEqual('object', typeof exif);
	assert.strictEqual('object', typeof exif.image);
	assert.strictEqual('number', typeof exif.image.XResolution);

[ompal-sisodiya]

@lovell All the required change are done on our end. could you review once.

[lovell]

@ompal-sisodiya Thanks for the updates. I don't see any verification of output image EXIF metadata in the newly-added tests; am I missing something? (I note you've added to an existing unit test, but that logic is unrelated to this PR, I was merely using it as an example of using exif-reader to parse the output.)

[ompal-sisodiya]

@lovell Thanks for your response. please review the below test for the verification of output image with EXIF metadata.
if this is fine then i will commit the code else you can help me with the test.

it('TIFF setting resolution unit(cm)', async () => {
    await sharp(fixtures.inputJpgWithExif)
      .tiff({ resolutionUnit: 'inch' })
      .metadata(function (err, metadata) {
        if (err) throw err;
        // EXIF
        assert.strictEqual('object', typeof metadata.exif);
        assert.strictEqual(true, metadata.exif instanceof Buffer);
        const exif = exifReader(metadata.exif);
        assert.strictEqual('object', typeof exif);
        assert.strictEqual('object', typeof exif.image);
        assert.strictEqual('number', typeof exif.image.XResolution);
        assert.strictEqual('number', typeof exif.image.ResolutionUnit);
      });
  });

[lovell]

@ompal-sisodiya Please can you add an assertion on the value of exif.image.ResolutionUnit (as well as the type).

[ompal-sisodiya]

@lovell I have added assertion for the value of resolution unit. could you review once.

[ompal-sisodiya]

@lovell Could please review PR?

[lovell]

Thanks again for taking the time to submit a PR, I will review this when I am ready to do so. Coordinated pestering won't make that happen any sooner.

[lovell]

Landed via commit f7bed69

I also added the (normalised) resolutionUnit property to the response from metadata(), which had the added advantage of making the tests a bit simpler.

This will be in v0.30.0, thanks again for the PR.