Has anyone written the code to save an `ImageBitmap` to the photos library on iOS via Kotlin? I'm lo...

# compose-ios

[Andrew Watson]

Has anyone written the code to save an ImageBitmap to the photos library on iOS via Kotlin? I'm looking around for a code sample but can't quite find it. I have some code but I get an odd null pointer exception:

actual fun saveBitmap(bmp: ImageBitmap) {
        PHPhotoLibrary.requestAuthorization { status ->
            if (status == PHAuthorizationStatusAuthorized) {
                PHPhotoLibrary.sharedPhotoLibrary().performChanges({

                    val bytes = bmp.asSkiaBitmap().readPixels()

                    bytes?.let { array ->
                        val nsData = array.toNSData()

                        val img = UIImage(data = nsData)

                        PHAssetChangeRequest.creationRequestForAssetFromImage(img)
                    }
                }, null)
            }
        }
    }

[Andrew Watson]

Update: I'm fairly certain the crash is happening when I'm trying to create the UIImage; I think I need to massage the pixel data but I'm unsure quite how to do that

[Alexander Maryanovsky]

Just guessing here, but what formats does UIImage expects to get? What you’re giving it is a raw array of pixels, but what it probably expects is JPEG/PNG data.

[Andrew Watson]

Yeah that's what I need to find out

[Andrew Watson]

The NSData bytearray probably has to probably be just so

[Alexander Maryanovsky]

Maybe try Image.makeFromBitmap(bmp.asSkiaBitmap()).encodeToData().bytes

[Andrew Watson]

I can do that!

[Alexander Maryanovsky]

That should give you a PNG

[Alexander Maryanovsky]

encodeToData takes a format argument if you want other formats

[Andrew Watson]

That did the trick!

[Andrew Watson]

Solution: this is the save method that works:

actual fun saveBitmap(bmp: ImageBitmap) {
        PHPhotoLibrary.requestAuthorization { status ->
            if (status == PHAuthorizationStatusAuthorized) {
                PHPhotoLibrary.sharedPhotoLibrary().performChanges({
                    val bytes = Image.makeFromBitmap(bmp.asSkiaBitmap()).encodeToData()!!.bytes
                    val nsData = bytes.toNSData()

                    val img = UIImage(data = nsData)
                    PHAssetChangeRequest.creationRequestForAssetFromImage(img)
                }, null)
            }
        }
    }

[Andrew Watson]

Thanks so much @Alexander Maryanovsky

[Dima Avdeev]

Also, we have code to save and read images in ImageViewer example here: https://github.com/JetBrains/compose-multiplatform/tree/master/examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/storage