View Filters

var View.filter: Filter? = null

ComposedFilter

You can apply several filters to a view using this:

class ComposedFilter(val filters: List<Filter>) : Filter()

IdentityFilter

This filter can be used to no apply filters at all. But serves for the subtree to be rendered in a texture. This is useful for example to change the alpha of a complex object as a whole, instead of affecting each alpha of the descendant views.

object IdentityFilter : Filter()

container {
	scale(0.8)
	position(24, 24)
	alpha = 0.25
	filter = IdentityFilter
	image(resourcesVfs["korge.avif"].readBitmap())
	image(resourcesVfs["korge.avif"].readBitmap()) {
		position(64, 64)
	}
}

ColorMatrixFilter

The color matrix filter allows to transform the colors in your views using a full 4x4 matrix. It already provides a computed matrix to show images as greyscale.

class ColorMatrixFilter(var colorMatrix: Matrix3D, var blendRatio: Double) : Filter() {
    companion object {
        val GRAYSCALE_MATRIX = Matrix3D.fromRows(
            0.33f, 0.33f, 0.33f, 0f,
            0.59f, 0.59f, 0.59f, 0f,
            0.11f, 0.11f, 0.11f, 0f,
            0f, 0f, 0f, 1f
        )
        
        val IDENTITY_MATRIX = Matrix3D.fromRows(
            1f, 0f, 0f, 0f,
            0f, 1f, 0f, 0f,
            0f, 0f, 1f, 0f,
            0f, 0f, 0f, 1f
        )
    }
}

view.filter = ColorMatrixFilter(ColorMatrixFilter.GRAYSCALE_MATRIX)

Convolute3Filter

Allows to apply 3x3 convolution filters (also called Kernel) in realtime to the View.

This filter exposes matrices for making 3x3 gaussian blurs, box blurs, and edge detection.

class Convolute3Filter(var kernel: Matrix3D) : Filter() {
    companion object {
        val KERNEL_GAUSSIAN_BLUR: Matrix3D
        val KERNEL_BOX_BLUR: Matrix3D
        val KERNEL_IDENTITY: Matrix3D
        val KERNEL_EDGE_DETECTION: Matrix3D
    }
}

view.filter = Convolute3Filter(Convolute3Filter.KERNEL_EDGE_DETECTION)

BlurFilter

Allows to apply a blur filter with an adjustable radius using the Kawase approximation algorithm.

class BlurFilter(initialRadius: Double = 1.0) : Filter {
    var radius: Double
}

view.filter = BlurFilter(8.0)

WaveFilter and PageFilter

Can be used to simulate pages from books:

class PageFilter(
    var hratio: Double = 0.5,
    var hamplitude0: Double = 0.0,
    var hamplitude1: Double = 10.0,
    var hamplitude2: Double = 0.0,
    var vratio: Double = 0.5,
    var vamplitude0: Double = 0.0,
    var vamplitude1: Double = 0.0,
    var vamplitude2: Double = 0.0
) : Filter()

view.filter = PageFilter(hamplitude1 = 64.0)

class WaveFilter(
    var amplitudeX: Int = 10,
    var amplitudeY: Int = 10,
    var crestCountX: Double = 2.0,
    var crestCountY: Double = 2.0,
    var cyclesPerSecondX: Double = 1.0,
    var cyclesPerSecondY: Double = 1.0,
    var time: Double = 0.0
) : Filter()

SwizzleColorsFilter

Serves to do component swizzling (RGBA) per pixel (that’s interchanging component colors):

class SwizzleColorsFilter(var swizzle: String = "rgba") : Filter()

view.filter = SwizzleColorsFilter("bgra")

DitheringFilter

It can simulate a dithering from a posterization:

view.filter = DitheringFilter(levels = 2.0)

Backdrop Filters

It is possible to render filters as backdrop

TODO

Custom Filters

KorGE supports creating custom filters by providing shader programs.