Fix RgbScalar

[stefannikolei]

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Description

I ran the tests with SSE Disabled. And I found this bug...

Before fixing it I had 151 failing tests after it only 53 tests are failing. On a quick check all other failures are 'Image difference is over threshold!'

[brianpopow]

We need a test to cover this issue. I will try to help here.

There are more color converter path's which are not covered by tests: ColorConverters. We need not add more unit tests there (@stefannikolei: not necessary you, btw).

[brianpopow]

I have added tests now to cover all path for JpegColorConverterBase

I think its ready for review now.

[antonfirsov]

LGTM for the fix.

I wonder now however, why do we have CmykArm64, while we don't have YCbCrArm64. Doesn't CmykArm64 and CmykVector have essentially the same performance?

[stefannikolei]

LGTM for the fix.

I wonder now however, why do we have CmykArm64, while we don't have YCbCrArm64. Doesn't CmykArm64 and CmykVector have essentially the same performance?

Ycbcr is implemented in #2417

You can check the performance in the prs. All have benchmarks attached

[antonfirsov]

Ycbcr is implemented in #2417

Ah for some reason I thought that was already merged 😄 With those numbers it makes sense thanks!