为什么当我创建位图时，它全是空的？
罗南·瓜塔（Ronen Gueta）
private Bitmap CropImage()
{
Bitmap pic = pictureBoxSnap.Image as Bitmap;
Bitmap cropped = new Bitmap(rect.Width, rect.Height);
using (Graphics g = Graphics.FromImage(cropped))
{
g.DrawImage(pic, new Rectangle(0, 0, rect.Width, rect.Height),
rect, GraphicsUnit.Pixel);
}
pic.Save(@"c:\temp\testingitimage.jpg");
cropped.Save(@"c:\temp\testingitimage1.bmp");
return cropped;
}
我添加了这两行保存来测试我得到了什么。我看到的第一个图片在pictureBox中是正确的图像。但是第二个作物全是白色和空的。
我从pictureBox绘画事件中调用此方法：
private void pictureBoxSnap_Paint(object sender, PaintEventArgs e)
{
if (pictureBoxSnap.Image != null)
{
{
if (ClearGraphics == false)
{
if (cropRect == false)
{
if (rectangles[listBoxSnap.SelectedIndex] != Rectangle.Empty)
{
e.Graphics.DrawRectangle(Pens.Firebrick, rectangles[listBoxSnap.SelectedIndex]);
}
}
else
{
if (rect.Width > 10 && rect.Height > 10)
{
e.Graphics.DrawRectangle(Pens.Gray, rect);
pictureBoxSnap.Image = CropImage();
Image img = CropImage();
img.Save(@"c:\temp\testimageing.jpg");
}
}
}
}
}
}
我在以下位置使用了一个断点：e.Graphics.DrawRectangle（Pens.Gray，rect）; 并且rect不为空（rect是Rectangle，我在pictureBox上绘制，然后当我单击按钮时，它对pictureBox进行验证）。
我也在这里进行了保存并进行了testimageing，我在硬盘上看到它是黑色的，但是当我用Paint编辑它时，我看到它是白色的。
例如，当我在pictureBox上绘制一个矩形时，我在CropImage方法中使用了一个断点，我看到变量rect例如：X = 136 Y = 149 Width = 131 Height = 106在绘制事件中，这个rect变量也具有相同的值。
并且pictureBox的大小为：640x480并且pictureBox属性的SizeMode设置为：zoom
我为什么得到空的白色图像？而不是其中部分图像位于内部的裁剪矩形吗？
编辑：
这是我现在使用的代码：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO;
using DannyGeneral;
using System.Diagnostics;
namespace MinimizeCapture
{
public partial class Form1 : Form
{
Boolean bHaveMouse;
Point ptOriginal = new Point();
Point ptLast = new Point();
bool cropRect;
Bitmap cloneBitmap;
Rectangle recttest;
private Rectangle Rect;
private Rectangle[] rectangles;
private Rectangle RectClone;
private bool btn = false;
private Point RectStartPoint = Point.Empty;
private Point RectEndPoint = Point.Empty;
private Brush selectionBrush = new SolidBrush(Color.Red);
private Pen pen;
private string selectedIndex;
private List<string> drawnItems = new List<string>();
private bool ClearGraphics;
public Form1()
{
InitializeComponent();
cropRect = false;
var windows = OpenWindowGetter.FindWindowsWithText();
ClearGraphics = false;
this.DoubleBuffered = true;
btn = false;
pen = new Pen(selectionBrush);
buttonSnap.Enabled = false;
backgroundWorker1.RunWorkerAsync();
}
private void buttonSnap_Click(object sender, EventArgs e)
{
ClearGraphics = true;
this.listBoxSnap.Items.Clear();
this.pictureBoxSnap.Image = null;
backgroundWorker1.RunWorkerAsync();
}
private void listBoxSnap_SelectedIndexChanged(object sender, EventArgs e)
{
WindowSnap snap = this.listBoxSnap.SelectedItem as WindowSnap;
selectedIndex = this.listBoxSnap.SelectedIndex.ToString();
this.pictureBoxSnap.Image = snap.Image;
for (int i = 0; i < rectangles.Length; i++)
{
if (rectangles[i] != RectClone)
{
ClearGraphics = false;
}
else
{
ClearGraphics = true;
}
}
}
private void checkBoxForceMDI_CheckedChanged(object sender, EventArgs e)
{
WindowSnap.ForceMDICapturing = (sender as CheckBox).Checked;
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
listBoxSnap.Invoke(new MethodInvoker(delegate { this.listBoxSnap.Items.Add("Minimized Windows"); }));
listBoxSnap.Invoke(new MethodInvoker(delegate { this.listBoxSnap.Items.AddRange(WindowSnap.GetAllWindows(true,true).ToArray()); }));
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
rectangles = new Rectangle[listBoxSnap.Items.Count];
buttonSnap.Enabled = true;
}
private void pictureBoxSnap_Paint(object sender, PaintEventArgs e)
{
if (pictureBoxSnap.Image != null)
{
{
if (ClearGraphics == false)
{
if (rectangles[listBoxSnap.SelectedIndex] != Rectangle.Empty)
{
e.Graphics.DrawRectangle(Pens.Firebrick, rectangles[listBoxSnap.SelectedIndex]);
}
}
if (cropRect == true)
{
if (recttest.Width > 10 && recttest.Height > 10)
{
//e.Graphics.DrawRectangle(Pens.Gray, recttest);
e.Graphics.Clear(Color.White);
/*pictureBoxSnap.Image = CropImage();
Image img = CropImage();
img.Save(@"c:\temp\testimageing.jpg");*/
}
}
}
}
}
private void pictureBoxSnap_MouseMove(object sender, MouseEventArgs e)
{
if (btn == true)
{
ClearGraphics = false;
RectEndPoint = e.Location;
int currentindex = listBoxSnap.SelectedIndex;
rectangles[currentindex] = RectClone;
Rect = getRect(RectStartPoint, RectEndPoint);
RectClone = Rect;
pictureBoxSnap.Invalidate();
}
Point ptCurrent = new Point(e.X, e.Y);
// If we "have the mouse", then we draw our lines.
if (bHaveMouse)
{
// If we have drawn previously, draw again in
// that spot to remove the lines.
if (ptLast.X != -1)
{
MyDrawReversibleRectangle(ptOriginal, ptLast);
}
// Update last point.
ptLast = ptCurrent;
// Draw new lines.
MyDrawReversibleRectangle(ptOriginal, ptCurrent);
}
}
private void pictureBoxSnap_MouseDown(object sender, MouseEventArgs e)
{
RectStartPoint = e.Location;
btn = true;
Rect = Rectangle.Empty;
RectClone = Rectangle.Empty;
bHaveMouse = true;
// Store the "starting point" for this rubber-band rectangle.
ptOriginal.X = e.X;
ptOriginal.Y = e.Y;
// Special value lets us know that no previous
// rectangle needs to be erased.
ptLast.X = -1;
ptLast.Y = -1;
}
private void pictureBoxSnap_MouseUp(object sender, MouseEventArgs e)
{
recttest = rectangles[listBoxSnap.SelectedIndex];
ClearGraphics = false;
btn = false;
RectEndPoint = e.Location;
pictureBoxSnap.Invalidate();
int currentindex = listBoxSnap.SelectedIndex;
rectangles[currentindex] = RectClone;
// Set internal flag to know we no longer "have the mouse".
bHaveMouse = false;
// If we have drawn previously, draw again in that spot
// to remove the lines.
if (ptLast.X != -1)
{
Point ptCurrent = new Point(e.X, e.Y);
MyDrawReversibleRectangle(ptOriginal, ptLast);
}
// Set flags to know that there is no "previous" line to reverse.
ptLast.X = -1;
ptLast.Y = -1;
ptOriginal.X = -1;
ptOriginal.Y = -1;
pictureBoxSnap.Invalidate();
}
Rectangle getRect(Point p1, Point p2)
{
Point p = new Point(Math.Min(p1.X, p2.X), Math.Min(p1.Y, p2.Y));
Size s = new Size(Math.Abs(p1.X - p2.X), Math.Abs(p1.Y - p2.Y));
return new Rectangle(p, s);
}
private void ConfirmRectangle_Click(object sender, EventArgs e)
{
ConfirmRectangle.ForeColor = Color.Red;
ConfirmRectangle.Enabled = false;
StreamWriter w = new StreamWriter(@"c:\temp\Settings.txt", true);
w.WriteLine("Rectangle Location: " + RectClone.Location + " Rectangle Size: " + RectClone.Size + " Selected Index: " + selectedIndex);
textBoxIndex.Text = selectedIndex.ToString();
w.Close();
cropRect = false;
//pictureBoxSnap.Invalidate();
Image img = CropImage();
img.Save(@"c:\temp\testimageing.jpg");
pictureBoxSnap.Image = img;
}
// Convert and normalize the points and draw the reversible frame.
private void MyDrawReversibleRectangle(Point p1, Point p2)
{
Rectangle rc = new Rectangle();
// Convert the points to screen coordinates.
p1 = pictureBoxSnap.PointToScreen(p1);
p2 = pictureBoxSnap.PointToScreen(p2);
// Normalize the rectangle.
if (p1.X < p2.X)
{
rc.X = p1.X;
rc.Width = p2.X - p1.X;
}
else
{
rc.X = p2.X;
rc.Width = p1.X - p2.X;
}
if (p1.Y < p2.Y)
{
rc.Y = p1.Y;
rc.Height = p2.Y - p1.Y;
}
else
{
rc.Y = p2.Y;
rc.Height = p1.Y - p2.Y;
}
// Draw the reversible frame.
rect = new Rectangle(pictureBoxSnap.PointToClient(rc.Location), rc.Size);
ControlPaint.DrawReversibleFrame(rc, Color.Gray, FrameStyle.Dashed);
}
Rectangle rect = Rectangle.Empty;
private Bitmap CropImage()
{
//rect = recttest;
Bitmap pic = pictureBoxSnap.Image as Bitmap;
Bitmap cropped = new Bitmap(rect.Width, rect.Height);
using (Graphics g = Graphics.FromImage(cropped))
{
g.DrawImage(pic, new Rectangle(0, 0, rect.Width, rect.Height),
rect, GraphicsUnit.Pixel);
}
pic.Save(@"c:\temp\testingitimage.jpg");
cropped.Save(@"c:\temp\testingitimage1.bmp");
return cropped;
}
}
}
将CropImage调用方法从绘画中移出，并将其添加到按钮上，单击此处：
private void ConfirmRectangle_Click(object sender, EventArgs e)
{
ConfirmRectangle.ForeColor = Color.Red;
ConfirmRectangle.Enabled = false;
StreamWriter w = new StreamWriter(@"c:\temp\Settings.txt", true);
w.WriteLine("Rectangle Location: " + RectClone.Location + " Rectangle Size: " + RectClone.Size + " Selected Index: " + selectedIndex);
textBoxIndex.Text = selectedIndex.ToString();
w.Close();
cropRect = false;
//pictureBoxSnap.Invalidate();
Image img = CropImage();
img.Save(@"c:\temp\testimageing.jpg");
pictureBoxSnap.Image = img;
}
这行：
Image img = CropImage();
img.Save(@"c:\temp\testimageing.jpg");
pictureBoxSnap.Image = img;
但是我在pictureBox中得到的是这样的：
不知道为什么。矩形位于我绘制的位置，但是可以显示原始图像在矩形中剪切的部分，就像放大一样。
γηράσκωδ'αείπολλάδιδασκόμε
private Bitmap CropImage(){
Bitmap pic = pictureBoxSnap.Image as Bitmap;
Bitmap cropped = new Bitmap(rect.Width, rect.Height);
using (Graphics g = Graphics.FromImage(cropped)){
g.DrawImage(pic, new Rectangle(0, 0, rect.Width, rect.Height),
rect, GraphicsUnit.Pixel);
}
using (Graphics g = Graphics.FromImage(pic)){
g.DrawImage(cropped , 136, 149, rect.Width, rect.Height);
//Draw the rectangle
}
//pic.Save(@"c:\temp\testingitimage.jpg");
//cropped.Save(@"c:\temp\testingitimage1.bmp");
return pic;
}
瓦尔特
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