c# - 使图像变亮/变暗/透明部分

Question

我正在将图像加载到 BitmapImage 中并将其转换为 PixelColor 的数组。我想要的是能够操纵这些像素中的一些，使它们更亮/更暗/透明，但我似乎无法让它工作。将其设置为某种颜色确实有效，但 alpha channel 会被忽略。

这是一个使用 C#4 的 WPF 应用

谢谢!
还有代码……

namespace BitmapTest {
using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using Image = System.Windows.Controls.Image;

public partial class MainWindow {
    public MainWindow() {
        InitializeComponent();
        LoadImage();
    }

    [DllImport("gdi32")]
    private static extern int DeleteObject(IntPtr o);

    public static BitmapSource LoadBitmap(Bitmap source) {
        var ip = source.GetHbitmap();
        try {
            return Imaging.CreateBitmapSourceFromHBitmap(ip,
                                                         IntPtr.Zero, Int32Rect.Empty,
                                                         BitmapSizeOptions.FromEmptyOptions());
        } finally {
            DeleteObject(ip);
        }
    }

    private void LoadImage() {
        var i = new Image();
        var src = new BitmapImage();
        src.BeginInit();
        src.UriSource = new Uri("road.jpg", UriKind.Relative);
        src.CacheOption = BitmapCacheOption.OnLoad;
        src.EndInit();

        var pixels = GetPixels(src);
        for (var x = 0; x < Math.Min(50, pixels.GetLength(0)); x++) {
            for (var y = 0; y < Math.Min(50, pixels.GetLength(1)); y++) {
                pixels[x, y] = new PixelColor {Alpha = 100, Red = pixels[x, y].Red, Green = pixels[x, y].Green, Blue = pixels[x, y].Blue};
            }
        }

        var bitmap = new WriteableBitmap(src.PixelWidth, src.PixelHeight, src.DpiX, src.DpiY, src.Format, src.Palette);
        PutPixels(bitmap, pixels, 0, 0);

        i.Source = bitmap;
        i.Stretch = Stretch.Fill;
        RootGrid.Children.Add(i);
    }

    public PixelColor[,] GetPixels(BitmapSource source) {
        if (source.Format != PixelFormats.Bgra32)
            source = new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0);

        var pixels = source.CopyPixels();
        return pixels;
    }

    public void PutPixels(WriteableBitmap bitmap, PixelColor[,] pixels, int x, int y) {
        var width = pixels.GetLength(0);
        var height = pixels.GetLength(1);
        var sourceRect = new Int32Rect(0, 0, width, height);
        bitmap.WritePixels(sourceRect, pixels, width*4, x, y);
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct PixelColor {
        public byte Blue;
        public byte Green;
        public byte Red;
        public byte Alpha;
    }
}


public static class BitmapSourceHelper {
    public static MainWindow.PixelColor[,] CopyPixels(this BitmapSource source) {
        if (source.Format != PixelFormats.Bgra32)
            source = new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0);
        var pixels = new MainWindow.PixelColor[source.PixelWidth, source.PixelHeight];
        var stride = source.PixelWidth * ((source.Format.BitsPerPixel + 7) / 8);
        var pinnedPixels = GCHandle.Alloc(pixels, GCHandleType.Pinned);
        source.CopyPixels(
            new Int32Rect(0, 0, source.PixelWidth, source.PixelHeight),
            pinnedPixels.AddrOfPinnedObject(),
            pixels.GetLength(0) * pixels.GetLength(1) * 4,
            stride);
        pinnedPixels.Free();
        return pixels;
    }
}
}

Answer 1

这是在 Windows 窗体应用程序中使图像变亮和变暗的示例。此处的代码基于代码项目网站上一篇文章的亮度过滤器部分:Image Processing for Dummies with C# and GDI+ Part 1 .

    public Bitmap Lighten(Bitmap bitmap, int amount)
{
  if (amount < -255 || amount > 255)
    return bitmap;

  // GDI+ still lies to us - the return format is BGR, NOT RGB.
  BitmapData bmData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

  int stride = bmData.Stride;
  System.IntPtr Scan0 = bmData.Scan0;

  int nVal = 0;

  unsafe
  {
    byte* p = (byte*)(void*)Scan0;

    int nOffset = stride - bitmap.Width * 3;
    int nWidth = bitmap.Width * 3;

    for (int y = 0; y < bitmap.Height; ++y)
    {
      for (int x = 0; x < nWidth; ++x)
      {
        nVal = (int)(p[0] + amount);

        if (nVal < 0) nVal = 0;
        if (nVal > 255) nVal = 255;

        p[0] = (byte)nVal;

        ++p;
      }
      p += nOffset;
    }
  }

  bitmap.UnlockBits(bmData);

  return bitmap;
}

private void btnLighten_Click(object sender, EventArgs e)
{
  Bitmap image = pictureBox1.Image as Bitmap;
  pictureBox1.Image = Lighten(image, 10);
}

private void btnDarken_Click(object sender, EventArgs e)
{
  Bitmap image = pictureBox1.Image as Bitmap;
  pictureBox1.Image = Lighten(image, -10);
}