PixelMap

ImageBitmapReadPixelsSample

@Sampled
fun ImageBitmapReadPixelsSample() {
    val imageBitmap = createImageBitmap()

    val buffer = IntArray(20 * 10)
    imageBitmap.readPixels(buffer = buffer, startX = 8, startY = 9, width = 20, height = 10)

    val pixelmap = PixelMap(buffer = buffer, width = 20, height = 10, stride = 20, bufferOffset = 0)

    // create a histogram to count the number of occurrences of a color within the specified
    // subsection of the provided ImageBitmap
    val histogram = HashMap<Color, Int>()
    for (x in 0 until pixelmap.width) {
        for (y in 0 until pixelmap.height) {
            val color = pixelmap[x, y]
            val colorCount = histogram[color] ?: 0
            histogram[color] = (colorCount + 1)
        }
    }
}

private fun createImageBitmap(): ImageBitmap {
    val imageBitmap = ImageBitmap(100, 100)
    val canvas = Canvas(imageBitmap)
    val paint = Paint()

    // Draw 4 colored squares that are red, blue, green and yellow from the top left, top right
    // bottom left and bottom right respectively
    paint.color = Color.Red
    canvas.drawRect(Rect(0.0f, 0.0f, 50.0f, 50.0f), paint)

    paint.color = Color.Blue
    canvas.drawRect(Rect(50.0f, 0.0f, 100.0f, 50.0f), paint)

    paint.color = Color.Green
    canvas.drawRect(Rect(0.0f, 50.0f, 50.0f, 100.0f), paint)

    paint.color = Color.Yellow
    canvas.drawRect(Rect(50.0f, 50.0f, 100.0f, 100.0f), paint)
    return imageBitmap
}