Helpful methods for converting to string.

[FelipeCoro]

As you know ImageBitmap might not be the best end result for some user in multiplatform, given its not platform independent.
I suggest adding this few lines in the readme, maybe further down the road as a function to help new users obtain a Base64 String they can use to easily store their signature.

commonMain:
expect fun ImageBitmap.toBase64(): String

androidMain:

actual fun ImageBitmap.toBase64(): String {
    val bitmap = this.asAndroidBitmap()
    val byteArrayOutputStream = ByteArrayOutputStream()
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream)
    val byteArray = byteArrayOutputStream.toByteArray()
    return Base64.encodeToString(byteArray, Base64.NO_WRAP)
}

iosMain:

@OptIn(ExperimentalForeignApi::class)
fun ImageBitmap.toUIImage(): UIImage? {
    val width = this.width
    val height = this.height
    val buffer = IntArray(width * height)

    this.readPixels(buffer)

    val colorSpace = CGColorSpaceCreateDeviceRGB()
    val context = CGBitmapContextCreate(
        data = buffer.refTo(0),
        width = width.toULong(),
        height = height.toULong(),
        bitsPerComponent = 8u,
        bytesPerRow = (4 * width).toULong(),
        space = colorSpace,
        bitmapInfo = CGImageAlphaInfo.kCGImageAlphaPremultipliedLast.value
    )

    val cgImage = CGBitmapContextCreateImage(context)
    return cgImage?.let { UIImage.imageWithCGImage(it) }
}

actual fun ImageBitmap.toBase64(): String {
    val uiImage = this.toUIImage()
    val jpegData = uiImage?.let { UIImageJPEGRepresentation(it, 0.5) }
        ?: return ""
    return jpegData.base64Encoding()
}

[joelkanyi]

Hey @FelipeCoro , thank you for this! I'll add it to the README and, later, create some utility functions for Sain to convert ImageBitmap to a String across all platforms, including Android, iOS, JVM, WASM, and JS.