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.net core 把一个图片缩略变小

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悬赏园豆：5 [待解决问题]

.net core 把一个图片缩略变小 .net core 把一个图片缩略变小  .net core 把一个图片缩略变小

凤城沙子的主页 凤城沙子 | 初学一级 | 园豆：112
提问于：2018-08-11 15:22
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所有回答(3)
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参考代码（需要安装 nuget 包 System.Drawing.Common）

using (Image originImage = Image.FromStream(originImageStream))
{
    using (var bitmap = new Bitmap(newWidth, newHeight))
    {
        using (var graphic = GetGraphic(originImage, bitmap))
        {
            graphic.DrawImage(originImage, 0, 0, newWidth, newHeight);
            using (var encoderParameters = new EncoderParameters(1))
            {
                using (var encoderParameter = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L))
                {
                    encoderParameters.Param[0] = encoderParameter;
                    bitmap.Save(newImageStream,
                                ImageCodecInfo.GetImageEncoders().Where(x => x.MimeType.Equals(mimeType, StringComparison.OrdinalIgnoreCase)).FirstOrDefault(),
                                encoderParameters);
                }
            }
        }
    }
}
dudu | 园豆：30994 (高人七级) | 2018-08-11 16:40
0

由于.net core缺乏基于图像的 API,所以需要引用第三方包

可以参数针对.NET Core的图像类库

缩放代码,引用的nuget包是ZKWeb.System.Drawing

        public static Image ZoomImage(Image image, int destWidth, int destHeight, string ext = "png") {
            try {
                var sourceImage = image;
                int width, height;
                var sourceWidth = sourceImage.Width;
                var sourceHeight = sourceImage.Height;
                if (sourceHeight > destHeight || sourceWidth > destWidth) {
                    if (sourceWidth * destHeight > sourceHeight * destWidth) {
                        width = destWidth;
                        height = destWidth * sourceHeight / sourceWidth;
                    } else {
                        height = destHeight;
                        width = sourceWidth * destHeight / sourceHeight;
                    }
                } else {
                    width = sourceWidth;
                    height = sourceHeight;
                }
                var destBitmap = new Bitmap(destWidth, destHeight);
                var g = Graphics.FromImage(destBitmap);
                g.Clear(ext == "png" ? Color.Transparent : Color.White);
                g.CompositingQuality = CompositingQuality.HighQuality;
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.InterpolationMode = InterpolationMode.HighQualityBicubic;
                g.DrawImage(sourceImage, new Rectangle((destWidth - width) / 2, (destHeight - height) / 2, width, height),
                    0, 0, sourceImage.Width, sourceImage.Height, GraphicsUnit.Pixel);
                g.Dispose();
                var encoderParams = new EncoderParameters();
                var quality = new long[1];
                quality[0] = 100;
                var encoderParam = new EncoderParameter(Quality, quality);
                encoderParams.Param[0] = encoderParam;
                sourceImage.Dispose();
                return destBitmap;
            } catch {
                return image;
            }
        }
远扬 | 园豆：30 (初学一级) | 2018-08-11 18:14

.NET Core 2.0 开始提供了 System.Drawing.Common

支持(0) 反对(0) dudu | 园豆：30994 (高人七级) | 2018-08-11 18:28

@dudu: 

好的~没了解

支持(0) 反对(0) 远扬 | 园豆：30 (初学一级) | 2018-08-11 19:21
0

skiasharp 这个组件挺好用的

通信的搞程序 | 园豆：1747 (小虾三级) | 2018-08-14 22:55
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