Confusion of the percentage definition

[bcjohnblue]

The result of percentage makes me confused.

It says 0.2 means the pixel difference is 0.2% from README.md.

cy.get('h1').compareSnapshot('homePage', 0.2) // will compare only the image of h1 element and fail only if the percentage of pixels that are different is bigger than 0.2%

However, the percentage doesn't multiple by 100 in source code. I think the range of percentage is from 0 to 1 now.

const percentage = (mismatchedPixels / diffImage.width / diffImage.height) ** 0.5

In conclusion, 0.2 should not translated to 0.2%, it means20%.

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By the way, I suggest to remove ** 0.5 when calculate percentage. It seems haim-io/cypress-image-diff#184 has similar request too.

[Zaista]

Thanks for raising the issue, you are right, it is confusing. It was always represented as a decimal range 0-1, and we've always referred to it as the percentage. In the following PR I reworded it a little bit to make it clearer and fixed my 0.2% mistake.

For the square root part, you are again right, removing ** 0.5 and calculating the percentage by hand gives the correct numbers, I can't imagine why it was there in the first place for a straightforward pixel difference calculation. @mjhea0 maybe you could weigh in on this one? 🤔

The PR should be ready soonish