@niivue/niivue/src/drawing/undo.ts

minimal webgl2 nifti image viewer

import { log } from '@/logger'
import { decodeRLE } from '@/drawing/rle'

interface DrawUndoArgs {
    drawUndoBitmaps: Uint8Array[]
    currentDrawUndoBitmap: number
    drawBitmap: Uint8Array
}
export const drawUndo = ({ drawUndoBitmaps, currentDrawUndoBitmap, drawBitmap }: DrawUndoArgs): { drawBitmap: Uint8Array; currentDrawUndoBitmap: number } | undefined => {
    const len = drawUndoBitmaps.length
    if (len < 1) {
        log.debug('undo bitmaps not loaded')
        return
    }
    currentDrawUndoBitmap--
    if (currentDrawUndoBitmap < 0) {
        currentDrawUndoBitmap = len - 1
    }
    if (currentDrawUndoBitmap >= len) {
        currentDrawUndoBitmap = 0
    }
    if (drawUndoBitmaps[currentDrawUndoBitmap].length < 2) {
        log.debug('drawUndo is misbehaving')
        return
    }
    drawBitmap = decodeRLE(drawUndoBitmaps[currentDrawUndoBitmap], drawBitmap.length)
    return { drawBitmap, currentDrawUndoBitmap }
}