Common/PictureHelper.cs

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


namespace Common
{
    public  class PictureHelper
    {

        /// 获取缩略图
        public static Image GetThumbnailImage(Image image, int width, int height)
        {
            if (image == null || width < 1 || height < 1)
                return null;

            // 新建一个bmp图片
            Image bitmap = new Bitmap(width, height);

            // 新建一个画板
            using (var g = Graphics.FromImage(bitmap))
            {
                // 设置高质量插值法
                g.InterpolationMode = InterpolationMode.HighQualityBicubic;
                // 设置高质量,低速度呈现平滑程度
                g.SmoothingMode = SmoothingMode.HighQuality;
                // 高质量、低速度复合
                g.CompositingQuality = CompositingQuality.HighQuality;
                // 清空画布并以透明背景色填充
                g.Clear(Color.Transparent);
                // 在指定位置并且按指定大小绘制原图片的指定部分
                g.DrawImage(image, new Rectangle(0, 0, width, height),
                    new Rectangle(0, 0, image.Width, image.Height),
                    GraphicsUnit.Pixel);
                return bitmap;
            }
        }

        /// <summary>
        ///     生成缩略图，并保持纵横比
        /// </summary>
        /// <returns>生成缩略图后对象</returns>
        public static Image GetThumbnailImageKeepRatio(Image image, int width, int height)
        {
            var imageSize = GetImageSize(image, width, height);
            return GetThumbnailImage(image, imageSize.Width, imageSize.Height);
        }

        /// <summary>
        ///     根据百分比获取图片的尺寸
        /// </summary>
        public static Size GetImageSize(System.Drawing.Image picture, int percent)
        {
            if (picture == null || percent < 1)
                return Size.Empty;
            var width = picture.Width * percent / 100;