在面板上绘制，保存为位图
本文关键字：保存 位图 绘制 | 更新日期: 2023-09-27 18:12:44
我想做一个简单的应用程序，用户可以在面板上绘制并将其保存到他们的计算机上作为位图。然而，当我进入保存部分时，我所得到的只是一个空的(白色)位图。
我一直在浏览许多其他解决方案，我很确定我以正确的方式保存位图，所以我开始怀疑我的绘图过程是否不正确。这里到底出了什么问题?
public partial class Form1 : Form
{
SolidBrush brush;
Pen pen;
Point[] points = new Point[3];
Graphics display;
Bitmap bmap;
public Form1()
{
InitializeComponent();
display = panel1.CreateGraphics();
bmap = new Bitmap(panel1.Width, panel1.Height);
}
private void panel1_MouseDown(object sender, MouseEventArgs e)
{
brush = new SolidBrush(Color.Black);
pen = new Pen(Color.Black);
display.FillEllipse(brush, e.X, e.Y, 10, 10);
panel1.DrawToBitmap(bmap, new Rectangle(0, 0, panel1.Width, panel1.Height));
//this.Invalidate();
}
private void clearToolStripMenuItem_Click(object sender, EventArgs e)
{
Graphics display = panel1.CreateGraphics();
display.Clear(panel1.BackColor);
}
private void saveToolStripMenuItem_Click(object sender, EventArgs e)
{
bmap.Save(@"C:'Temp'Test.bmp");
}
}
编辑修改后，我只得到一个黑色的bmp，我甚至看不到在我的屏幕上创建的省略号了。虽然我确实注意到，如果我把无效和绘制位图回到mousedown事件，那么保存按钮将保存最后一个椭圆，而仍然没有出现在我的屏幕上。
private void panel1_MouseDown(object sender, MouseEventArgs e)
{
mousedown = true;
x = e.X;
y = e.Y;
}
private void panel1_Paint(object sender, PaintEventArgs e)
{
//Graphics g = e.Graphics;
if(mousedown==true)
{
brush = new SolidBrush(Color.Black);
pen = new Pen(Color.Black);
Graphics.FromImage(bmap).FillEllipse(brush, x, y, 10, 10);
panel1.Invalidate();
//panel1.DrawToBitmap(bmap, new Rectangle(0, 0, panel1.Width, panel1.Height));
//panel1.Invalidate();
}
}
Hans在他的注释中完成了大部分工作，下面是您的代码应该看起来的样子:
public partial class Form1 : Form {
Bitmap bmap;
public Form1() {
InitializeComponent();
bmap = new Bitmap(panel1.ClientWidth, panel1.ClientHeight);
panel1.MouseDown += panel1_MouseDown;
panel1.Paint += panel1_Paint;
}
void panel1_Paint(object sender, PaintEventArgs e) {
e.Graphics.DrawImage(bmap, Point.Empty);
}
void panel1_MouseDown(object sender, MouseEventArgs e) {
using (Graphics g = Graphics.FromImage(bmap)) {
g.FillEllipse(Brushes.Black, e.X, e.Y, 10, 10);
}
panel1.Invalidate();
}
private void clearToolStripMenuItem_Click(object sender, EventArgs e) {
using (Graphics g = Graphics.FromImage(bmap)) {
g.Clear(Color.White);
}
panel1.Invalidate();
}
private void saveToolStripMenuItem_Click(object sender, EventArgs e) {
bmap.Save(@"c:'temp'bmap.bmp");
}
}
CreateGraphics只是一个临时画布，因此您很少(如果有的话)将其用于绘图目的，特别是当您试图保存图像时。
可以正常工作。我测试了一下，效果很好
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace drawing
{
public partial class Form2 : Form
{
Graphics g;
bool startPaint = false;
int? initX = null;
int? initY = null;
bool drawSquare = false;
bool drawRectangle = false;
bool drawCircle = false;
public Form2()
{
InitializeComponent();
bmp = new Bitmap(panel1.ClientSize.Width, panel1.ClientSize.Height);
}
Bitmap bmp;
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
}
void panel1_MouseMove(object sender, MouseEventArgs e)
{
if (startPaint)
{
using ( g = Graphics.FromImage(bmp))
{
// g.FillEllipse(Brushes.Black, new Rectangle(e.X, e.Y , 5, 5));
Pen p = new Pen(btn_PenColor.BackColor, float.Parse(cmb_PenSize.Text));
g.DrawLine(p, new Point(initX ?? e.X, initY ?? e.Y), new Point(e.X, e.Y));
initX = e.X;
initY = e.Y;
//g.DrawImage(bmp, new Rectangle(e.X - 4, e.Y - 4, 8, 8));
}
panel1.Invalidate();
}
}
private void pnl_Draw_MouseDown(object sender, MouseEventArgs e)
{
startPaint = true;
if (drawSquare)
{
//Use Solid Brush for filling the graphic shapes
SolidBrush sb = new SolidBrush(btn_PenColor.BackColor);
//setting the width and height same for creating square.
//Getting the width and Heigt value from Textbox(txt_ShapeSize)
g.FillRectangle(sb, e.X, e.Y, int.Parse(txt_ShapeSize.Text), int.Parse(txt_ShapeSize.Text));
//setting startPaint and drawSquare value to false for creating one graphic on one click.
startPaint = false;
drawSquare = false;
}
if (drawRectangle)
{
SolidBrush sb = new SolidBrush(btn_PenColor.BackColor);
//setting the width twice of the height
g.FillRectangle(sb, e.X, e.Y, 2 * int.Parse(txt_ShapeSize.Text), int.Parse(txt_ShapeSize.Text));
startPaint = false;
drawRectangle = false;
}
if (drawCircle)
{
SolidBrush sb = new SolidBrush(btn_PenColor.BackColor);
g.FillEllipse(sb, e.X, e.Y, int.Parse(txt_ShapeSize.Text), int.Parse(txt_ShapeSize.Text));
startPaint = false;
drawCircle = false;
}
}
private void pnl_Draw_MouseUp(object sender, MouseEventArgs e)
{
startPaint = false;
initX = null;
initY = null;
}
void panel1_Paint(object sender, PaintEventArgs e)
{
e.Graphics.DrawImage(bmp, Point.Empty);
}
private void button1_Click(object sender, EventArgs e)
{
bmp.Save("D://filename.jpg", ImageFormat.Png);
}
}
}