apewer-dotnet/Apewer/DrawingUtility.cs

#if DRAWING

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace Apewer
{

    /// <summary>绘图。</summary>
    public static class DrawingUtility
    {

        /// <summary>优化 Graphics 对象的属性，提升绘图质量。</summary>
        public static Graphics Optimize(this Graphics graphics)
        {
            if (graphics != null)
            {
                graphics.CompositingMode = CompositingMode.SourceOver;
                graphics.CompositingQuality = CompositingQuality.HighQuality;
                graphics.SmoothingMode = SmoothingMode.AntiAlias;
            }
            return graphics;
        }

        /// <summary>保存图像为文件。</summary>
        /// <exception cref="ArgumentNullException"></exception>
        public static byte[] Save(this Image image, ImageFormat format)
        {
            if (image == null) throw new ArgumentNullException(nameof(image));
            if (format == null) throw new ArgumentNullException(nameof(format));

            using (var memory = new MemoryStream())
            {
                image.Save(memory, format);
                return memory.ToArray();
            }
        }

        /// <summary>保存为 JPEG 文件。</summary>
        /// <param name="image">Image 实例。</param>
        /// <param name="quality">JPEG 质量，0 为最低质量，100 为最高质量。</param>
        /// <exception cref="ArgumentNullException" />
        /// <exception cref="ArgumentOutOfRangeException" />
        /// <exception cref="System.Runtime.InteropServices.ExternalException" />
        public static byte[] SaveAsJpeg(this Image image, int quality = 100)
        {
            if (image == null) throw new ArgumentNullException(nameof(image));
            if (quality < 0 || quality > 100) throw new ArgumentOutOfRangeException(nameof(quality));

            var codec = ImageCodecInfo.GetImageDecoders().Find(x => x.FormatID == ImageFormat.Jpeg.Guid);
            if (codec == null) throw new System.Runtime.InteropServices.ExternalException($"系统中不存在 JPEG 编码器。");

            var parameters = new EncoderParameters(1);
            parameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);

            using (var memory = new MemoryStream())
            {
                image.Save(memory, codec, parameters);
                return memory.ToArray();
            }
        }

        /// <summary>缩放图像，生成新图像。</summary>
        /// <param name="image">原始图像。</param>
        /// <param name="size">新图像的大小。</param>
        /// <param name="backgroundColor">填充新图像背景色。</param>
        /// <exception cref="ArgumentNullException"></exception>
        /// <exception cref="ArgumentOutOfRangeException"></exception>
        public static Bitmap Scale(this Image image, Size size, Color? backgroundColor = null) => Scale(image, size.Width, size.Height, backgroundColor);

        /// <summary>缩放图像，生成新图像。</summary>
        /// <param name="image">原始图像。</param>
        /// <param name="width">新图像的宽度。</param>
        /// <param name="height">新图像的高度。</param>
        /// <param name="backgroundColor">填充新图像背景色。</param>
        /// <exception cref="ArgumentNullException"></exception>
        /// <exception cref="ArgumentOutOfRangeException"></exception>
        static Bitmap Scale(this Image image, int width, int height, Color? backgroundColor = null)
        {
            if (image == null) throw new ArgumentNullException(nameof(image));
            if (width < 1) throw new ArgumentOutOfRangeException(nameof(width));
            if (height < 1) throw new ArgumentOutOfRangeException(nameof(height));

            // 检查原始图像是否为透明格式
            var rawFormat = image.RawFormat;
            var isTransparentFormat = rawFormat.Equals(ImageFormat.Png) || rawFormat.Equals(ImageFormat.Gif);
            var pixelFormat = isTransparentFormat ? PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb;

            var bitmap = new Bitmap(width, height, pixelFormat);
            try
            {
                using (var graphic = Graphics.FromImage(bitmap))
                {
                    graphic.CompositingMode = CompositingMode.SourceOver;
                    graphic.CompositingQuality = CompositingQuality.HighQuality;
                    graphic.SmoothingMode = SmoothingMode.AntiAlias;

                    // 填充背景色
                    if (isTransparentFormat)
                    {
                        if (backgroundColor != null && backgroundColor.HasValue) graphic.Clear(backgroundColor.Value);
                    }

                    // 绘制新图像
                    graphic.DrawImage(image, 0, 0, width, height);
                }
                return bitmap;
            }
            catch
            {
                bitmap.Dispose();
                throw;
            }
        }

    }

}

#endif