c# - WPF - Graphics.CopyFromScreen 返回尺寸错误的图像

问题描述

使用 WPF，我想截取一个由矩形定义的区域的屏幕截图，该矩形(x,y)代表左上角，以及矩形的width和height。

在此示例中，source屏幕截图的矩形由左上角定义，source.x=0 和 source.y=0，source.width=200 和 source.height=200。

为了确保该功能执行我想要的操作，我将屏幕截图作为图像显示在屏幕上。source我在 position的矩形旁边显示屏幕截图的图像destination。在本例中，destination由destination.x = source.x + source.width (=200)、destination.y=0、destination.width 和destination.height = 200 定义。

这是应用程序的最小工作示例：

<Window x:Class="ScreenViewerWPF.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ScreenViewerWPF"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800"
        
        WindowState="Maximized"
        Topmost="True"
        AllowsTransparency="True"  WindowStyle="None"
        >
    <Window.Background>
        <SolidColorBrush Opacity="0.5" Color="White"/>
    </Window.Background>
    <Grid Name="grid">
    </Grid>
</Window>

using System;
using System.Drawing;
using System.Drawing.Imaging;
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;

namespace ScreenViewerWPF
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            var source = new
            {
                top = 0,
                left = 0,
                width = 200,
                height = 200
            };
            var dest = new
            {
                top = 0,
                left = 200,
                width = 200,
                height = 200
            };
            //rectangle to visualize the source
            grid.Children.Add(new System.Windows.Shapes.Rectangle()
            {
                Margin = new Thickness(source.left, source.top, 0, 0),
                Width = source.width,
                Height = source.height,
                Stroke = new SolidColorBrush(System.Windows.Media.Color.FromRgb(255, 0, 0)),
                HorizontalAlignment = HorizontalAlignment.Left,
                VerticalAlignment = VerticalAlignment.Top,
            });
            // rectangle to visualize the destination
            grid.Children.Add(new System.Windows.Shapes.Rectangle()
            {
                Margin = new Thickness(dest.left, dest.top, 0, 0),
                Width = dest.width,
                Height = dest.height,
                Stroke = new SolidColorBrush(System.Windows.Media.Color.FromRgb(0, 0, 255)),
                HorizontalAlignment = HorizontalAlignment.Left,
                VerticalAlignment = VerticalAlignment.Top,
            });

            Bitmap bmp = new Bitmap(120*source.width/96, 120 * source.height/96);
            Graphics g = Graphics.FromImage(bmp);
            g.CopyFromScreen(source.left, source.top, 0, 0, bmp.Size);
            bmp.Save("test.jpg", ImageFormat.Jpeg);
            // grabed image
            Image image = new()
            {
                Margin = new Thickness(dest.left, dest.top, 0, 0),
                Width = dest.width,
                Height = dest.height,
                HorizontalAlignment = HorizontalAlignment.Left,
                VerticalAlignment = VerticalAlignment.Top,
            }; grid.Children.Add(image);
            BitmapSource bitmapSource = Imaging.CreateBitmapSourceFromHBitmap(
                bmp.GetHbitmap(),
                IntPtr.Zero,
                Int32Rect.Empty,
                BitmapSizeOptions.FromWidthAndHeight(source.width, source.height)
             );
            image.Source = bitmapSource;
        }
        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);
            MakeClicThrough();
        }

        #region make the window clic-through able
        // this is for being able to clic through the form
        [DllImport("user32.dll", SetLastError = true)]
        static extern int GetWindowLong(IntPtr hWnd, int nIndex);
        [DllImport("user32.dll")]
        static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
        const int GWL_EXSTYLE = -20;
        const int WS_EX_LAYERED = 0x80000;
        const int WS_EX_TRANSPARENT = 0x20;
        private void MakeClicThrough()
        {
            var hwnd = new WindowInteropHelper(this).Handle;
            var style = GetWindowLong(hwnd, GWL_EXSTYLE);
            SetWindowLong(hwnd, GWL_EXSTYLE, style | WS_EX_LAYERED | WS_EX_TRANSPARENT);
        }
        #endregion
    }
}

请注意这一行Bitmap bmp = new Bitmap(120*source.width/96, 120 * source.height/96);，这是我用来“尝试”以使事情正常进行的修复。120 是我的计算机 DPI，96 是常数 DPI。

如果没有120/96，我会得到这个（运行应用程序时屏幕左上角的屏幕截图）：

可以看出，两张图片不匹配，右边一张像是“放大了”。

有了 ratio 120/96，我得到了这个，它更好但还不够好（如您所见，第 41 行在右图的图像中，而在左边它位于矩形下方。

我想在矩形中有“完全”的好图像（或尽可能接近）。如果可能的话，一个优雅的解决方案。

标签： c#wpfgraphicsbitmapscreenshot

c# - WPF - Graphics.CopyFromScreen 返回尺寸错误的图像

问题描述

解决方案

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