WinForm（十二）画图

在.NET中，画图主要是通过Graphics类实现的，这个类主要通过两类方法完成画图，一类是DrawXXX，画各种线条图形；另一类是FillXXX,用各种形状，填充各种图形。Graphics是画板，Draw各个方法是各种盏笔（不过在调用Draw方法时，参数需要一个Pen对象)，Fill的各个方法就是种种刷子（确实Fill的方法参数也需要一个Brush对象）。首先要熟悉各个Draw和Fill方法，以及他们的参数，那么剩下的事就是对坐票了，画什么，在那里画，怎么用Draw和Fill了。

下面是在Form上画了一个小票，然后调用打印组件在虚拟打印机里打印出来的效果。.

using QRCoder;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;
namespace WinFormsDemo12{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        void Draw(Graphics graphics)        {            var y = 15;            using var logo = new Bitmap(Directory.GetCurrentDirectory() + "/aeon.png");            graphics.DrawImage(MakeGrayscale(logo), 60, y, 200, 80);            graphics.DrawLine(new Pen(Color.Black, 2), 10, y += 80, 310, y);            graphics.DrawLine(new Pen(Color.Black, 2), 10, y += 4, 310, y);            var font = new Font("黑体", 10);            var brush = new SolidBrush(Color.Black);            graphics.DrawString("分店：012", font, brush, 10, y += 1);            graphics.DrawString("店员：张三", font, brush, 160, y);            graphics.DrawString($"时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}", font, brush, 10, y += 20);            var no = "000000000001";            graphics.DrawString($"流水号：{no}", font, brush, 10, y += 20);            graphics.DrawLine(new Pen(Color.Black, 2), 10, y += 25, 310, y);            graphics.DrawString("名称       数量  单价  金额", font, brush, 10, y += 5);            graphics.DrawString("西红柿     500g  26.00 15.00", font, brush, 10, y += 20);            graphics.DrawString("西葫芦    1000g  23.00 23.00", font, brush, 10, y += 20);            graphics.DrawString("茄子       500g  50.00 25.00", font, brush, 10, y += 20);            graphics.DrawString("豆角       500g  38.00 19.00", font, brush, 10, y += 20);            graphics.DrawLine(new Pen(Color.Black, 2), 10, y += 20, 310, y);            graphics.DrawLine(new Pen(Color.Black, 2), 10, y += 4, 310, y);            var sumfont = new Font("黑体", 12);            graphics.DrawString("              小计：82", sumfont, brush, 10, y += 5);
            var qrCodeAsBitmapByteArr = PngByteQRCodeHelper.GetQRCode(no, QRCodeGenerator.ECCLevel.Q, 20, false);            using var qrcode = Image.FromStream(new MemoryStream(qrCodeAsBitmapByteArr));            graphics.DrawImage(qrcode, 100, y += 50, 120, 120);        }
        public static Bitmap MakeGrayscale(Bitmap original)        {            var newBitmap = new Bitmap(original.Width, original.Height);            var g = Graphics.FromImage(newBitmap);            var colorMatrix = new System.Drawing.Imaging.ColorMatrix(               new float[][]              {                  new float[] {.3f, .3f, .3f, 0, 0},                  new float[] {.59f, .59f, .59f, 0, 0},                  new float[] {.11f, .11f, .11f, 0, 0},                  new float[] {0, 0, 0, 1, 0},                  new float[] {0, 0, 0, 0, 1}              });            var attributes = new System.Drawing.Imaging.ImageAttributes();            attributes.SetColorMatrix(colorMatrix);            g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height), 0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);            g.Dispose();            return newBitmap;        }           private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)        {            if (e.Graphics != null)            {                Draw(e.Graphics);            }        }        private void button2_Click(object sender, EventArgs e)        {            printDocument1.Print();        }        private void button1_Click(object sender, EventArgs e)        {            var graphics = this.CreateGraphics();            Draw(graphics);        }    }}

MakeGrayscale方法是把彩色logo转黑白的一个算法，关注画图部分请忽略。

Graphics实现了IDisposable，用后请释放。

窗体的浏览效果：

WinForm（十二）画图

虚拟打印机输出的PDF效果图：

WinForm（十二）画图

董川民