protected fun filterRowWithFilterType()

in plot-api/src/commonMain/kotlin/org/jetbrains/letsPlot/util/pngj/pixels/PixelsWriter.kt [121:194]
69 lines of code
9 McCabe index (conditional complexity)

    protected fun filterRowWithFilterType(
        _filterType: FilterType, _rowb: ByteArray, _rowbprev: ByteArray,
        _rowf: ByteArray
    ): ByteArray {
        // warning: some filters rely on: "previous row" (rowbprev) it must be initialized to 0 the first time
        @Suppress("NAME_SHADOWING")
        var _rowf = _rowf
        if (_filterType === FilterType.FILTER_NONE) _rowf = _rowb
        _rowf[0] = _filterType.value.toByte()
        var i: Int
        var j: Int
        when (_filterType) {
            FilterType.FILTER_NONE -> {}
            FilterType.FILTER_PAETH -> {
                i = 1
                while (i <= bytesPixel) {
                    _rowf[i] =
                        PngHelperInternal.filterRowPaeth(_rowb[i].toInt(), 0, _rowbprev[i].toInt() and 0xFF, 0).toByte()
                    i++
                }
                j = 1
                i = bytesPixel + 1
                while (i <= bytesRow) {
                    _rowf[i] = PngHelperInternal.filterRowPaeth(
                        _rowb[i].toInt(), _rowb[j].toInt() and 0xFF, _rowbprev[i].toInt() and 0xFF,
                        _rowbprev[j].toInt() and 0xFF
                    ).toByte()
                    i++
                    j++
                }
            }

            FilterType.FILTER_SUB -> {
                i = 1
                while (i <= bytesPixel) {
                    _rowf[i] = _rowb[i]
                    i++
                }
                j = 1
                i = bytesPixel + 1
                while (i <= bytesRow) {
                    _rowf[i] = (_rowb[i] - _rowb[j]).toByte()
                    i++
                    j++
                }
            }

            FilterType.FILTER_AVERAGE -> {
                i = 1
                while (i <= bytesPixel) {
                    _rowf[i] = (_rowb[i] - (_rowbprev[i].toInt() and 0xFF) / 2).toByte()
                    i++
                }
                j = 1
                i = bytesPixel + 1
                while (i <= bytesRow) {
                    _rowf[i] = (_rowb[i] - ((_rowbprev[i].toInt() and 0xFF) + (_rowb[j].toInt() and 0xFF)) / 2).toByte()
                    i++
                    j++
                }
            }

            FilterType.FILTER_UP -> {
                i = 1
                while (i <= bytesRow) {
                    _rowf[i] = (_rowb[i] - _rowbprev[i]).toByte()
                    i++
                }
            }

            else -> throw PngjOutputException("Filter type not recognized: $_filterType")
        }
        return _rowf
    }