* add ImageFilterTest.kt: blur test

* add ImageFilterTest.kt: AlphaThreshold

* add ImageFilterTest.kt: Arithmetic

* add ImageFilterTest.kt: small refactoring

* add ImageFilterTest.kt: blend

* add ImageFilterTest.kt: colorFilter

* add ImageFilterTest.kt: compose

* add ImageFilterTest.kt: displacementMap

* add ImageFilterTest.kt: dropShadow

* add ImageFilterTest.kt: dropShadowOnly

* add ImageFilterTest.kt: makeImage

* add ImageFilterTest.kt: magnifier

* add ImageFilterTest.kt: MatrixConvolution

* add ImageFilterTest.kt: MatrixTransform

* add ImageFilterTest.kt: makeMerge

* add ImageFilterTest.kt: makeOffset

* add ImageFilterTest.kt: makePaint

* add ImageFilterTest.kt: makeTile

* add ImageFilterTest.kt: makeDilate

* add ImageFilterTest.kt: makeErode

* add ImageFilterTest.kt: makeDistantLitDiffuse

* add ImageFilterTest.kt: makePointLitDiffuse

* add ImageFilterTest.kt: makeSpotLitDiffuse

* add ImageFilterTest.kt: makeDistantLitSpecular

* add ImageFilterTest.kt: makePointLitSpecular

* add ImageFilterTest.kt: makeSpotLitSpecular
Co-authored-by: Oleksandr Karpovich <oleksandr.karpovich@jetbrains.com>