ImageBitmap

Graphics object that represents a 2 dimensional array of pixel information represented as ARGB values

Summary

Nested types

Provide an empty companion object to hang platform-specific companion extensions onto.

Public functions
Unit

Builds caches associated with the ImageBitmap that are used for drawing it.
Cmn
Unit
readPixels(
    buffer: IntArray,
    startX: Int,
    startY: Int,
    width: Int,
    height: Int,
    bufferOffset: Int,
    stride: Int
)

Copies the pixel data within the ImageBitmap into the given array.
Cmn

Public properties
ColorSpace

ColorSpace the Image renders in
Cmn
ImageBitmapConfig

Returns the current configuration of this Image, either:
Cmn
Boolean

Determines whether or not the ImageBitmap contains an alpha channel
Cmn
Int

The number of image pixels along the ImageBitmap's vertical axis.
Cmn
Int

The number of image pixels along the ImageBitmap's horizontal axis.
Cmn

Extension functions
Bitmap
android
PixelMap
ImageBitmap.toPixelMap(
    startX: Int,
    startY: Int,
    width: Int,
    height: Int,
    buffer: IntArray,
    bufferOffset: Int,
    stride: Int
)

Convenience method to extract pixel information from the given ImageBitmap into a PixelMap that supports for querying pixel information based on
Cmn

Public functions

prepareToDraw

Cmn
Added in 1.0.0
fun prepareToDraw(): Unit

Builds caches associated with the ImageBitmap that are used for drawing it. This method can be used as a signal to upload textures to the GPU to eventually be rendered

readPixels

Cmn
Added in 1.0.0
fun readPixels(
    buffer: IntArray,
    startX: Int = 0,
    startY: Int = 0,
    width: Int = this.width,
    height: Int = this.height,
    bufferOffset: Int = 0,
    stride: Int = width
): Unit

Copies the pixel data within the ImageBitmap into the given array. Each value is represented as ARGB values packed into an Int. The stride parameter allows the caller to allow for gaps in the returned pixels array between rows. For normal packed, results, the stride value is equivalent to the width of the ImageBitmap. The returned colors are non-premultiplied ARGB values in the ColorSpaces.Srgb color space.

Note this method can block so it is recommended to not invoke this method in performance critical code paths

import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.PixelMap

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)
    }
}
Parameters
buffer: IntArray

The array to store the ImageBitmap's colors. By default this allocates an IntArray large enough to store all the pixel information. Consumers of this API are advised to use the smallest IntArray necessary to extract relevant pixel information, that is the 2 dimensional area of the section of the ImageBitmap to be queried.
startX: Int = 0

The x-coordinate of the first pixel to read from the ImageBitmap
startY: Int = 0

The y-coordinate of the first pixel to read from the ImageBitmap
width: Int = this.width

The number of pixels to read from each row
height: Int = this.height

The number of rows to read
bufferOffset: Int = 0

The first index to write into the buffer array, this defaults to 0
stride: Int = width

The number of entries in buffer to skip between rows (must be >= width

Public properties

colorSpace

Cmn
Added in 1.0.0
val colorSpace: ColorSpace

ColorSpace the Image renders in

config

Cmn
Added in 1.0.0
val config: ImageBitmapConfig

Returns the current configuration of this Image, either:

See also
Argb8888
Rgb565
Alpha8
Gpu

hasAlpha

Cmn
Added in 1.0.0
val hasAlpha: Boolean

Determines whether or not the ImageBitmap contains an alpha channel

height

Cmn
Added in 1.0.0
val height: Int

The number of image pixels along the ImageBitmap's vertical axis.

width

Cmn
Added in 1.0.0
val width: Int

The number of image pixels along the ImageBitmap's horizontal axis.

Extension functions

asAndroidBitmap

android 
fun ImageBitmap.asAndroidBitmap(): Bitmap
Throws
kotlin.UnsupportedOperationException

if this ImageBitmap is not backed by an android.graphics.Bitmap

toPixelMap

Cmn 
fun ImageBitmap.toPixelMap(
    startX: Int = 0,
    startY: Int = 0,
    width: Int = this.width,
    height: Int = this.height,
    buffer: IntArray = IntArray(width * height),
    bufferOffset: Int = 0,
    stride: Int = width
): PixelMap

Convenience method to extract pixel information from the given ImageBitmap into a PixelMap that supports for querying pixel information based on

Note this method can block so it is recommended to not invoke this method in performance critical code paths

import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.PixelMap
import androidx.compose.ui.graphics.toPixelMap

val imageBitmap = createImageBitmap()

// Sample a 3 by 2 subsection of the given ImageBitmap
// starting at the coordinate (48, 49)
val pixelmap = imageBitmap.toPixelMap(startX = 48, startY = 49, width = 3, height = 2)

// 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)
    }
}
Parameters
startX: Int = 0

The x-coordinate of the first pixel to read from the ImageBitmap
startY: Int = 0

The y-coordinate of the first pixel to read from the ImageBitmap
width: Int = this.width

The number of pixels to read from each row
height: Int = this.height

The number of rows to read
buffer: IntArray = IntArray(width * height)

The array to store the ImageBitmap's colors. By default this allocates an IntArray large enough to store all the pixel information. Consumers of this API are advised to use the smallest IntArray necessary to extract relevant pixel information
bufferOffset: Int = 0

The first index to write into the buffer array, this defaults to 0
stride: Int = width

The number of entries in buffer to skip between rows (must be >= width
See also
readPixels