Question

我使用此代码创建缩略图，然后将原始缩略图存储到数据库中。它创建的tn始终是固定大小的，如果原始图像枯萎而不是更高，则将其剪切，然后调整为固定大小。

代码正在运行但是我真的很感激一些帮助修改此代码以执行以下操作（我已经尝试过但没有成功）：

制作高质量的缩略图
如果图像更高，则剪切高度比它的宽度（如果宽度是
200px和高度是1000px将是什么发生？）
接受png和tiff。

这是到目前为止的代码：

    public void imgUpload()
    {
        if (ImgUpload.PostedFile != null)
        {
            System.Drawing.Image image_file = System.Drawing.Image.FromStream(ImgUpload.PostedFile.InputStream);
            string fileName = Server.HtmlEncode(ImgUpload.FileName);
            string extension = System.IO.Path.GetExtension(fileName);

            bool sizeError = false;

            if(image_file.Width < 200)
                sizeError = true;

            if(image_file.Height < 250)
                sizeError = true;

            if ((extension.ToUpper() == ".JPG") && !sizeError)
            {

                //**** Resize image section ****  
                int image_height = image_file.Height;
                int image_width = image_file.Width;
                int original_width = image_width;
                int original_height = image_height;
                int max_height = 250;
                int max_width = 200;

                Rectangle rect;

                if (image_width > image_height)
                {
                    image_width = (image_width * max_height) / image_height;
                    image_height = max_height;
                    rect = new Rectangle(((image_width - max_width) / 2), 0, max_width, max_height);
                }
                else
                {
                    image_height = (image_height * max_width) / image_width;
                    image_width = max_width;
                    rect = new Rectangle(0, ((image_height - max_height) / 2), max_width, max_height);
                }

                Bitmap bitmap_file = new Bitmap(image_file, image_width, image_height);
                Bitmap new_bitmap_file = bitmap_file.Clone(rect, bitmap_file.PixelFormat);

                System.IO.MemoryStream stream = new System.IO.MemoryStream();

                new_bitmap_file.Save(stream, System.Drawing.Imaging.ImageFormat.Jpeg);
                stream.Position = 0;

                byte[] imageThumbnail = new byte[stream.Length + 1];
                stream.Read(imageThumbnail, 0, imageThumbnail.Length);

                Bitmap Original_bitmap_file = new Bitmap(image_file, original_width, original_height);
                System.IO.MemoryStream Original_stream = new System.IO.MemoryStream();

                Original_bitmap_file.Save(Original_stream, System.Drawing.Imaging.ImageFormat.Jpeg);
                Original_stream.Position = 0;

                byte[] imageOriginal = new byte[Original_stream.Length + 1];
                Original_stream.Read(imageOriginal, 0, imageOriginal.Length);
                //**** End resize image section ****  

                saveImage(imageThumbnail, imageOriginal, IDTextBox.Text);
                lblOutput.Visible = false;
            }
            else
            {
                lblOutput.Text = "Please only upload .jpg files and make sure the size is minimum 200x250";
                lblOutput.Visible = true;
            }
        }
        else
        {
            lblOutput.Text = "No file selected";
            lblOutput.Visible = true;
        }
    }

Answer 1

以下是如何缩放和裁剪图像的示例：

Bitmap b = new Bitmap(200, 1000);
using (var g = Graphics.FromImage(b))
{
    g.DrawLine(Pens.White, 0, 0, b.Width, b.Height);
}
b.Save("b.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

Bitmap thumb = new Bitmap(100, 100);
using (var g = Graphics.FromImage(thumb))
{
    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    g.DrawImage(b, new Rectangle(0,0,100,100), new Rectangle(0, 400, 200, 200), GraphicsUnit.Pixel);
}
thumb.Save("thumb.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

我认为你可以调整代码以适应所有内容以及当比率高度/宽度高时等等。

Answer 2

在为http://www.inventerat.se和其他一些网站创建缩略图时，我使用以下代码，它就像魅力一样：

    public static Bitmap WithinMaxSize(Image imgPhoto, int maxWidth, int maxHeight)
    {
        int sourceWidth = imgPhoto.Width;
        int sourceHeight = imgPhoto.Height;

        int destWidth;
        int destHeight;

        float sourceAspect = sourceWidth / (sourceHeight * 1.0F);
        float maxAspect = maxWidth / (maxHeight * 1.0F);
        if (sourceAspect > maxAspect)
        {
            // Width is limiting.
            destWidth = maxWidth;
            destHeight = (int)Math.Round(destWidth / sourceAspect);
        }
        else
        {
            // Height is limiting.
            destHeight = maxHeight;
            destWidth = (int)Math.Round(destHeight * sourceAspect);
        }

        Bitmap bmPhoto = new Bitmap(destWidth, destHeight);

        Graphics grPhoto = Graphics.FromImage(bmPhoto);
        grPhoto.Clear(Color.White);
        grPhoto.CompositingMode = CompositingMode.SourceCopy;
        grPhoto.CompositingQuality = CompositingQuality.HighQuality;
        grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

        grPhoto.DrawImage(imgPhoto, 0, 0, destWidth, destHeight);

        grPhoto.Dispose();
        return bmPhoto;
    }

请不要忘记处理从此方法返回的Bitmap。

如果用户上传非常大的图片（例如，> 5000 * 5000像素），则效果不佳。如果这是一项要求，我建议使用ImageMagick或类似的成像包。

要接受png和tiff，只需调整检查文件扩展名的方式，以便接受“png”，“tif”和“tiff”。支持tiff在.NET中有点粗略，因为tiff本身只是许多不同编码的容器。

缩略图，剪切调整大小并上传到DB

2 个答案: