fis_lib_vid/lib/processors/contrast.dart

import 'dart:typed_data';

import 'base.dart';

/// Vid对比度处理器
class VidContrastProcessor extends VidFrameProcessor {
  VidContrastProcessor(this.contrast) {
    _setActualContrast();
  }

  /// 对比度 [-99~99]
  final int contrast;

  late final double _actualContrast;

  void _setActualContrast() {
    double value = contrast.toDouble();
    if (value < -100) value = -100;
    if (value > 100) value = 100;
    value = (100.0 + value) / 100.0;
    value *= value;

    _actualContrast = value;
  }

  @override
  Uint8List process(Uint8List bytes, int position) {
    final i = position;
    final _contrast = _actualContrast;

    double b = bytes[i].toDouble();
    double g = bytes[i + 1].toDouble();
    double r = bytes[i + 2].toDouble();

    //process b
    b = b / 255.0;
    b -= 0.5;
    b *= _contrast;
    b += 0.5;
    b *= 255;
    if (b < 0) b = 0;
    if (b > 255) b = 255;

    //process g
    g = g / 255.0;
    g -= 0.5;
    g *= _contrast;
    g += 0.5;
    g *= 255;
    if (g < 0) g = 0;
    if (g > 255) g = 255;

    //process r
    r = r / 255.0;
    r -= 0.5;
    r *= _contrast;
    r += 0.5;
    r *= 255;
    if (r < 0) r = 0;
    if (r > 255) r = 255;

    bytes[i] = b.toInt();
    bytes[i + 1] = g.toInt();
    bytes[i + 2] = r.toInt();

    return bytes;
  }

  @override
  String toString() => 'VidContrastProcessor: $contrast';
}