FormXLetterbox
data class FormXLetterbox(val sourceWidth: Int = 0, val sourceHeight: Int = 0, val targetWidth: Int = 0, val targetHeight: Int = 0, val scale: Float = 0.0f, val offsetX: Int = 0, val offsetY: Int = 0, val scaledWidth: Int = 0, val scaledHeight: Int = 0)
FormXLetterbox contains the information of how to letterbox a source image to a target image