Set a gray filter in Skia

[Heidi Kurz]

Hi, I'm upgrating our Skia version from a old branch to the newest Skia version.

Now I have the problem that we set a gray filter like here:

SkPaint skpaint;

... do anything

Old code

 const SkScalar grayscale[20] = {

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // red

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // green

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // blue

        0.0f,  0.0f,  0.0f,  1.0f,  0.0f }; // alpha transparency

skpaint.setColorFilter(SkColorFilter::MakeMatrixFilterRowMajor255(grayscale));

But the method 

SkColorFilter::MakeMatrixFilterRowMajor255(...)

is removed. 

So far I was not able to find any replacement.

Please could anybody give me any hint how I could this functionality replace?

[Mike Klein]

There are a few SkColorFilters::Matrix() methods for this sort of color filter in SkColorFilter.h.

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[Heidi Kurz]

I tried out this 

 const SkScalar rowMajorgrayScale[20] = {

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // red

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // green

        0.21f, 0.72f, 0.07f, 0.0f, 100.0f, // blue

        0.0f,  0.0f,  0.0f,  1.0f,  0.0f }; // alpha transparency

 sk_sp<SkColorFilter> cf = SkColorFilters::Matrix(rowMajorgrayScale);

 skpaint.setColorFilter(cf);

But it doesn't work!

[Heidi Kurz]

I have played around a lot and found this solution 

 const SkScalar greyColorMatrix[20] = { 0.21f,  0.72f,  0.07f,    0.41f, 0, // red

                                     0.21f,  0.72f,  0.07f,    0.41f, 0,  // green

                                     0.21f,  0.72f,  0.07f,    0.41f, 0,  // blue

                                     0,    0,    0,    1.0f, 0 };

sk_sp<SkColorFilter> cf = SkColorFilters::Matrix(rowMajorgrayScale);

 skpaint.setColorFilter(cf);

That works.