Convert Base64 to PNG-File and save on Ktor Backende - kotlin

Question

I need to save an image from the Client App as PNG on the Backend.
Im sending the Image as Base64 with Post to the Backend.
I cant find a way to convert the Base64 String to an PNG File and dont know, how I could save them as File on the Server.
Thats the function I use to get the Data from the client. In val picture I get the Image as Base64.
fun savepicture(data: getpicture) =
transaction {
val userid= data.userid
val date = data.date
val time = data.time
val picture= data.picture
println("$picture")
try {
decodeImage(aufnahme)
}
catch(e: Exception) {
println("Fehler: $e")
}
if (picture.isNotEmpty()) {
return#transaction true
}
return#transaction false
}
fun decodeImage(image: String) {
val pictureBytes = Base64.getDecoder().decode(image)
val path = Path("Path/to/destination")
path.writeBytes(pictureBytes)
}
With this function i create the Base64 String. The Bitmap is created of a picture taken form the Device.
fun encodeImage(bm: Bitmap): String? {
val baos = ByteArrayOutputStream()
bm.compress(Bitmap.CompressFormat.PNG, 90, baos)
val b = baos.toByteArray()
return java.util.Base64.getEncoder().encodeToString(b)
}
I hope someone could help me to convert and save my image.

Answer 1

You can use java.util.Base64 to decode your base64 string into bytes. Then you'll need to write the bytes into a file.
For instance:
val picture: String = "the base64 data here as a string"
// decode the base64 text into bytes
val pictureBytes = Base64.getDecoder().decode(picture)
// write the bytes to a file
val path = Path("the/path/to/the/file.png")
path.writeBytes(pictureBytes)