如何在C#中为WPF在JPG上绘制矩形

Question

[！[在此处输入图像描述][1]][1]我有一个文件夹，里面有一系列jpg，这些是已转换为jpg的视频帧。我编写了一些代码，对它们进行迭代并显示。

我正试图在C#的JPG图像上画一个绿色的方框。Hight、Width、XC和YC在XML中，我只是访问每帧的数据。我使用位图使其工作，但要在WPF中显示它，我必须先将其转换为位图图像。问题是它需要很长的时间。我希望视频以每秒25帧的速度播放。所以所有的处理都需要在40毫秒内完成。现在，显示新图像需要0.01到0.3秒的时间。

这是我到目前为止的代码-

public void UpdateImage(string imageName, int[] boxData)
{

// imageName is the file path the image
Bitmap oldImage = new Bitmap(imageName);

// if objects are detected
if (boxData.Length != 0)
{
// transforms x and y cords to align box better to light
int newXC = boxData[0] - (boxData[2] / 2);
int newYC = boxData[1] - (boxData[3] / 2);
// ensures cords are not negative
if (newXC < 0)
newXC = 0;
if (newYC < 0)
newYC = 0;
// uses the DrawRectangleBorder to draw rectangles 
Bitmap newImage = DrawRectangleBorder(oldImage, new Rectangle(new System.Drawing.Point(newXC, newYC), new System.Drawing.Size(boxData[2], boxData[3])), Color.Green);
// converts Bitmap to BitmapImage
using (MemoryStream memory = new MemoryStream())
{
newImage.Save(memory, ImageFormat.Png);
memory.Position = 0;
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = memory;
bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
bitmapImage.EndInit();
ImportImage.Source = bitmapImage;
}
}
else
{
Bitmap newImage = oldImage;
// converts Bitmap to BitmapImage
using (MemoryStream memory = new MemoryStream())
{
newImage.Save(memory, ImageFormat.Png);
memory.Position = 0;
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = memory;
bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
bitmapImage.EndInit();
ImportImage.Source = bitmapImage;
}
}
}

DrawRectangleBorder方法-

private static Bitmap DrawRectangleBorder(Bitmap image, Rectangle rectangle, Color colour)
{
// makes new blank Bitmap from the old ones width and height
Bitmap newBitmap = new Bitmap(image.Width, image.Height);
// opens up the blank bit
using (Graphics graphics = Graphics.FromImage(newBitmap))
graphics.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height),
new Rectangle(0, 0, image.Width, image.Height), GraphicsUnit.Pixel);
// what actually draws the rectangles
for (Int32 x = rectangle.Location.X; x <= rectangle.Right && x < image.Width; x++)
for (Int32 y = rectangle.Location.Y; y <= rectangle.Bottom && y < image.Height; y++)
if (y == rectangle.Location.Y || y == rectangle.Bottom || x == rectangle.Location.X || x == rectangle.Right)
newBitmap.SetPixel(x, y, colour);
return newBitmap;
}

这是其中一张照片的样子，它们的分辨率是640乘480-[1] ：https://i.stack.imgur.com/ZiocC.jpg任何帮助都会很棒！

Answer 1

使用此XAML 可以简化代码

<Canvas>
<Image x:Name="ImportImage"/>
<Path x:Name="ObjectBox"
Width="{Binding ActualWidth, ElementName=ImportImage}"
Height="{Binding ActualHeight, ElementName=ImportImage}"
Stretch="None" Stroke="Green" StrokeThickness="1"/>
</Canvas>

使用类似这样的UpdateImage方法：

public void UpdateImage(string imagePath, int[] boxData)
{
ImportImage.Source = new BitmapImage(new Uri(imagePath));
var boxes = new GeometryGroup();
for (int i = 0; i <= boxData.Length - 4; i += 4)
{
int width = boxData[i + 2];
int height = boxData[i + 3];
int x = boxData[i] - width / 2;
int y = boxData[i + 1] - height / 2;
boxes.Children.Add(new RectangleGeometry(new Rect(x, y, width, height)));
}
ObjectBox.Data = boxes;
}

Answer 2

这里是一个使用覆盖在图像前面的矩形并控制其位置和大小的粗略演示。抱歉，以前从未在SO上分享过wpf，但我想这段代码就是你所需要的。我测试了时间，它可以远低于40ms(但我根本没有更新图像，只是矩形覆盖。如果需要的话，我也找到了这个快速视频显示WPF，但ya，没有实现或测试它。

&"；。cs"；

namespace ImageStreamer
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
Stopwatch stopWatch = new Stopwatch();
long lastTime = 0;
public MainWindow()
{
InitializeComponent();

dispatcherTimer.Tick += dispatcherTimer_Tick;
dispatcherTimer.Interval = new TimeSpan(0, 0, 0,0,25);
stopWatch.Start();
}
private void dispatcherTimer_Tick(object sender, EventArgs e)
{
targetRect.Margin = new Thickness(targetRect.Margin.Left+1, targetRect.Margin.Top+1,0,0);
targetRect.Width += 1;
targetRect.Height += 1;
Trace.WriteLine(lastTime - stopWatch.ElapsedMilliseconds);
lastTime = stopWatch.ElapsedMilliseconds;
}
private void Grid_Initialized(object sender, EventArgs e)
{
}
private void Button_Click(object sender, RoutedEventArgs e)
{
dispatcherTimer.Start();
}
}
}

"xaml"；

<Window x:Class="ImageStreamer.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:ImageStreamer"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid Initialized="Grid_Initialized">
<Image x:Name="imgBox" HorizontalAlignment="Left" Height="265" Margin="166,87,0,0" VerticalAlignment="Top" Width="512" Source="/ZiocC.jpg"/>
<Rectangle x:Name="targetRect" HorizontalAlignment="Left" Height="49" Margin="323,228,0,0" Stroke="Red" VerticalAlignment="Top" Width="113" StrokeThickness="5"/>
<Button Content="Button" HorizontalAlignment="Left" Margin="24,43,0,0" VerticalAlignment="Top" Click="Button_Click"/>
</Grid>
</Window>