Bitmap filter for uikit in image viewer sample

experimental/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/ImageViewer.ios.kt

@@ -11,6 +11,9 @@ import example.imageviewer.model.ContentRepository
 import example.imageviewer.model.State
 import example.imageviewer.model.adapter
 import example.imageviewer.model.createNetworkRepository
+import example.imageviewer.model.filtration.BlurFilter
+import example.imageviewer.model.filtration.GrayScaleFilter
+import example.imageviewer.model.filtration.PixelFilter
 import example.imageviewer.style.ImageViewerTheme
 import example.imageviewer.view.Toast
 import example.imageviewer.view.ToastState
@@ -39,18 +42,12 @@ internal fun ImageViewerIos() {
     }
 }
 
-class StubFilter : BitmapFilter {
-    override fun apply(bitmap: ImageBitmap): ImageBitmap {
-        return bitmap
-    }
-}
-
-private fun getDependencies(ioScope: CoroutineScope, toastState: MutableState<ToastState>) = object : Dependencies {
+fun getDependencies(ioScope: CoroutineScope, toastState: MutableState<ToastState>) = object : Dependencies {
     override val ioScope: CoroutineScope = ioScope
     override fun getFilter(type: FilterType): BitmapFilter = when (type) {
-        FilterType.GrayScale -> StubFilter()
-        FilterType.Pixel -> StubFilter()
-        FilterType.Blur -> StubFilter()
+        FilterType.GrayScale -> GrayScaleFilter()
+        FilterType.Pixel -> PixelFilter()
+        FilterType.Blur -> BlurFilter()
     }
 
     override val localization: Localization = object : Localization {

experimental/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/model/filtration/BlurFilter.kt

@@ -0,0 +1,13 @@
+package example.imageviewer.model.filtration
+
+import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.asComposeImageBitmap
+import androidx.compose.ui.graphics.asSkiaBitmap
+import example.imageviewer.core.BitmapFilter
+import example.imageviewer.utils.applyBlurFilter
+
+class BlurFilter : BitmapFilter {
+	override fun apply(bitmap: ImageBitmap): ImageBitmap {
+		return applyBlurFilter(bitmap.asSkiaBitmap()).asComposeImageBitmap()
+	}
+}

experimental/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/model/filtration/GrayScaleFilter.kt

@@ -0,0 +1,13 @@
+package example.imageviewer.model.filtration
+
+import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.asComposeImageBitmap
+import androidx.compose.ui.graphics.asSkiaBitmap
+import example.imageviewer.core.BitmapFilter
+import example.imageviewer.utils.applyGrayScaleFilter
+
+class GrayScaleFilter : BitmapFilter {
+	override fun apply(bitmap: ImageBitmap): ImageBitmap {
+		return applyGrayScaleFilter(bitmap.asSkiaBitmap()).asComposeImageBitmap()
+	}
+}

experimental/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/model/filtration/PixelFilter.kt

@@ -0,0 +1,13 @@
+package example.imageviewer.model.filtration
+
+import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.asComposeImageBitmap
+import androidx.compose.ui.graphics.asSkiaBitmap
+import example.imageviewer.core.BitmapFilter
+import example.imageviewer.utils.applyPixelFilter
+
+class PixelFilter : BitmapFilter {
+	override fun apply(bitmap: ImageBitmap): ImageBitmap {
+		return applyPixelFilter(bitmap.asSkiaBitmap()).asComposeImageBitmap()
+	}
+}

experimental/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/utils/GraphicsMath.ios.kt

@@ -0,0 +1,75 @@
+package example.imageviewer.utils
+
+import org.jetbrains.skia.*
+
+fun scaleBitmapAspectRatio(
+	bitmap: Bitmap,
+	width: Int,
+	height: Int
+): Bitmap {
+	val boundWidth = width.toFloat()
+	val boundHeight = height.toFloat()
+
+	val ratioX = boundWidth / bitmap.width
+	val ratioY = boundHeight / bitmap.height
+	val ratio = if (ratioX < ratioY) ratioX else ratioY
+
+	val resultWidth = (bitmap.width * ratio).toInt()
+	val resultHeight = (bitmap.height * ratio).toInt()
+
+	val result = Bitmap().apply {
+		allocN32Pixels(resultWidth, resultHeight)
+	}
+	val canvas = Canvas(result)
+	canvas.drawImageRect(Image.makeFromBitmap(bitmap), result.bounds.toRect())
+	canvas.readPixels(result, 0, 0)
+	canvas.close()
+
+	return result
+}
+
+fun applyGrayScaleFilter(bitmap: Bitmap): Bitmap {
+	val imageInfo = ImageInfo(
+		width = bitmap.width,
+		height = bitmap.height,
+		colorInfo = ColorInfo(ColorType.GRAY_8, ColorAlphaType.PREMUL, null)
+	)
+	val result = Bitmap().apply {
+		allocPixels(imageInfo)
+	}
+
+	val canvas = Canvas(result)
+	canvas.drawImageRect(Image.makeFromBitmap(bitmap), bitmap.bounds.toRect())
+	canvas.readPixels(result, 0, 0)
+	canvas.close()
+
+	return result
+}
+
+fun applyPixelFilter(bitmap: Bitmap): Bitmap {
+	val width = bitmap.width
+	val height = bitmap.height
+
+	var result = scaleBitmapAspectRatio(bitmap, width / 20, height / 20)
+	result = scaleBitmapAspectRatio(result, width, height)
+
+	return result
+}
+
+fun applyBlurFilter(bitmap: Bitmap): Bitmap {
+	val result = Bitmap().apply {
+		allocN32Pixels(bitmap.width, bitmap.height)
+	}
+	val blur = Paint().apply {
+		imageFilter = ImageFilter.makeBlur(10f, 10f, FilterTileMode.CLAMP)
+	}
+
+	val canvas = Canvas(result)
+	canvas.saveLayer(null, blur)
+	canvas.drawImageRect(Image.makeFromBitmap(bitmap), bitmap.bounds.toRect())
+	canvas.restore()
+	canvas.readPixels(result, 0, 0)
+	canvas.close()
+
+	return result
+}