How can i convert base64 to bitmap in compose multiplatform? whats the alternative of `android.graph...

# compose-ios

[Shoaib khalid]

How can i convert base64 to bitmap in compose multiplatform?
whats the alternative of android.graphics.BitmapFactory ?

[Michael Paus]

That’s how I do it in my code:

import org.jetbrains.skia.Image

	val PNG_BASE64_HEADER = "data:image/png;base64,"

    @OptIn(ExperimentalEncodingApi::class)
    private fun resolveImage(imgBase64: String?): ByteArray? {
        try {
            return imgBase64?.let {
                if (it.startsWith(PNG_BASE64_HEADER)) {
                    Base64.Default.decode(it.replaceFirst(PNG_BASE64_HEADER,""))
                } else {
                    log.debug { "Unknown image format: '${imgBase64.take(20)}'" }
                    null
                }
            }
        } catch (e: Exception) {
            throw Exception("Could not resolve image from base 64 string.", e)
        }
    }
    
    fun imageBitmapFromBytes(encodedImageData: ByteArray): ImageBitmap {
        return Image.makeFromEncoded(encodedImageData).toComposeImageBitmap()
    }

Should also work on iOS but I haven’t tested it there.

[Shoaib khalid]

thank you Michael, but i get an error on Image.makeFromEncoded...
Function invocation 'Image(...)' expected

[Shoaib khalid]

did you also face that?

[Michael Paus]

No. This is the original code (copied directly from some other project) which I use for iOS.

override fun imageBitmapFromBytes(encodedImageData: ByteArray): ImageBitmap {
        return Image.makeFromEncoded(encodedImageData).toComposeImageBitmap()
    }

Check the import statement for Image

import org.jetbrains.skia.Image

This code is of course platform specific, so you can’t use it in common.

[Shoaib khalid]

ahh i'm looking for any common main which could work on both android and ios. btw thanks

[Michael Paus]

On Android you would just use this corresponding code variant.

override fun imageBitmapFromBytes(encodedImageData: ByteArray): ImageBitmap {
    return BitmapFactory.decodeByteArray(encodedImageData, 0, encodedImageData.size).asImageBitmap()
}

In my code these variants are part of a class which is declared via expect/actual. You can then call imageBitmapFromBytes in your common code.

[Shoaib khalid]

It works, thank you. ❤️