C# GDI+开发手记

创建画布
画字体
文字区域内居中换行
文字在整个画布中居中
画直线
画圆形头像
压缩保存图片
缩放旋转
单位换算

创建画布

Bitmap image = new Bitmap(640, 1136, PixelFormat.Format32bppArgb);
//获得画布，设置高质量抗锯齿相关参数
Graphics g = Graphics.FromImage(image);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
//g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

画字体

//获得字体
string path = @"c:HUAKANGZUOJINHEIW8.TTF";
//读取字体文件            
PrivateFontCollection pfc = new PrivateFontCollection();
pfc.AddFontFile(path);
//实例化字体            
System.Drawing.Font printFont = new System.Drawing.Font(pfc.Families[0], 50, FontStyle.Regular);
System.Drawing.Font printFont2 = new System.Drawing.Font(pfc.Families[0], 30, FontStyle.Regular);
System.Drawing.Font printFont3 = new System.Drawing.Font("微软雅黑", 20, FontStyle.Regular);
g.DrawString("永恒钻石", font, Brushes.Black, 546, 186);

文字区域内居中换行

//字体在区域居中
StringFormat sf = new StringFormat();
sf.LineAlignment = StringAlignment.Center;
sf.Alignment = StringAlignment.Center;
Rectangle stringRect = new Rectangle(0, 50, 640, 276);
g.DrawString(name, printFont, Brushes.Black, stringRect, sf);

文字在整个画布中居中

计算居中坐标即可

//画名字
SizeF str_size = g.MeasureString(name, printFont);
g.DrawString(name, printFont, Brushes.White, (int)(320 - (str_size.Width / 2)), 285);
Pen p = new Pen(Color.White, 5);

画直线

Pen p = new Pen(Color.White, 5);
g.DrawLine(p, (int)(320 - (str_size.Width / 2)), 285 + str_size.Height, (int)(320 + (str_size.Width / 2)), 285 + str_size.Height);

画圆形头像

//画头像
//获得线笔
Pen pen = new Pen(Color.White, 5);
//新建个圆形路径
GraphicsPath gp = new GraphicsPath();
gp.AddEllipse(0, 0, 300, 300);
//先获得头像
Bitmap avator = new Bitmap(GetHttpBitmap(txurl), 300, 300);
//再新建个头像画布，把头像画上去
Bitmap avator_bp = new Bitmap(avator.Width, avator.Height);
using (Graphics gg = Graphics.FromImage(avator_bp))
{
    //圆形剪辑路径区域，类似于遮罩
    gg.SetClip(gp);
    gg.DrawImage(avator, 0, 0);
    gg.Dispose();
}
//画头像的圈圈
g.DrawEllipse(pen, 210, 30, 220, 220);
g.DrawImage(avator_bp, 220, 40, 200, 200);
bpp.Dispose();
bppp.Dispose();

压缩保存图片

        public static ImageCodecInfo GetEncoder(ImageFormat format)
        {
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.FormatID == format.Guid)
                {
                    return codec;
                }
            }
            return null;
        }

//唯一名称
string guid = Guid.NewGuid().ToString("N");

//设置JPG压缩级别
ImageCodecInfo jgpEncoder = Utils.GetEncoder(ImageFormat.Jpeg);
//见https://msdn.microsoft.com/en-us/library/system.drawing.imaging.encoder(v=vs.110).aspx
System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
EncoderParameters myEncoderParameters = new EncoderParameters(1);
EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 95L);
myEncoderParameters.Param[0] = myEncoderParameter;

//可以上传阿里云
using (MemoryStream ms = new MemoryStream())
{
    image.Save(ms, jgpEncoder, myEncoderParameters);
}
return guid;

缩放旋转

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Linq;
using System.Web;

namespace ImageUtils
{
    public static class EditImage
    {
        public static Bitmap ScaleImage(Bitmap img, float scalefactor)
        {
            Size size = new Size((int)(img.Width * scalefactor), (int)(img.Height * scalefactor));
            Bitmap bp = new Bitmap(img, size);
            return bp;
        }

        public static Bitmap RotateImage(Bitmap bmp, float angle, Color bkColor)
        {
            int w = bmp.Width + 2;
            int h = bmp.Height + 2;

            PixelFormat pf;

            if (bkColor == Color.Transparent)
            {
                pf = PixelFormat.Format32bppArgb;
            }
            else
            {
                pf = bmp.PixelFormat;
            }

            Bitmap tmp = new Bitmap(w, h, pf);
            Graphics g = Graphics.FromImage(tmp);
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.Clear(bkColor);
            g.DrawImageUnscaled(bmp, 1, 1);
            g.Dispose();

            GraphicsPath path = new GraphicsPath();
            path.AddRectangle(new RectangleF(0f, 0f, w, h));
            Matrix mtrx = new Matrix();
            mtrx.Rotate(angle);//矩阵变换
            RectangleF rct = path.GetBounds(mtrx);//获取边界

            Bitmap dst = new Bitmap((int)rct.Width, (int)rct.Height, pf);
            g = Graphics.FromImage(dst);
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.Clear(bkColor);
            g.TranslateTransform(-rct.X, -rct.Y);//因为rct的值为负
            g.RotateTransform(angle);
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;//.HighQualityBilinear;
            g.DrawImageUnscaled(tmp, 0, 0);
            g.Dispose();

            tmp.Dispose();

            return dst;
        }
    }
}

单位换算

/// <summary>
/// 毫米转为像素(注：dpi分水平和垂直，获取方法为得到 Graphics 的实例化对象 g，调用g.DpiX、g.DpiY)
/// </summary>
/// <param name="mm">毫米</param>
/// <param name="fDPI">分辨率(水平/垂直)</param>
/// <returns></returns>
public static float MillimetersToPixel(float mm, float fDPI)
{
    //毫米转像素：mm * dpi / 25.4 
    return (float)Math.Round((mm * fDPI / 25.4f), 2);
}
/// <summary>
/// 像素转为毫米(注：dpi分水平和垂直，获取方法为得到 Graphics 的实例化对象 g，调用g.DpiX、g.DpiY)
/// </summary>
/// <param name="px">像素</param>
/// <param name="fDPI">分辨率(水平/垂直)</param>
/// <returns></returns>
public static float PixelToMillimeters(float px, float fDPI)
{
    //像素转毫米：px * 25.4 / dpi
    return (float)Math.Round(((px * 25.4f) / fDPI), 2); ;
}
/// <summary>
/// 英寸到像素
/// </summary>
/// <param name="inches"></param>
/// <returns></returns>
public static float InchesToPixels(float inches, float fDPI)
{
    return (float)Math.Round(inches * fDPI, 2);
}
/// <summary>
/// 像素到英寸
/// </summary>
/// <param name="px"></param>
/// <returns></returns>
public static float PixelsToInches(float px, float fDPI)
{
    return (float)Math.Round(px / fDPI, 2);
}
/// <summary>
/// 毫米到英寸
/// </summary>
/// <param name="mm"></param>
/// <returns></returns>
public static float MillimetersToInches(float mm)
{
    return (float)Math.Round(mm / 25.4f, 2);
}
/// <summary>
/// 英寸到毫米
/// </summary>
/// <param name="mm"></param>
/// <returns></returns>
public static float InchesToMillimeters(float Inches)
{
    return (float)Math.Round(Inches * 25.4f, 2);
}