剪切图像的中心

时间:2012-04-20 08:29:55

标签: c# image image-processing

假设我有一个400x300px的图像,我想在服务器端(C#,.NET 4.0)将其剪切为200x200px的中心位置。

我该怎么办?使用一种画布并移动它?任何教程/代码示例/建议?

3 个答案:

答案 0 :(得分:5)

尝试这样的事情:

        Bitmap sourceImage = ...;

        int targetWidth = 200;
        int targetHeight = 200;

        int x = sourceImage.Width / 2 - targetWidth / 2;
        int y = sourceImage.Height / 2 - targetHeight / 2;

        Rectangle cropArea = 
            new Rectangle(x, y, targetWidth, targetHeight);

        Bitmap targetImage = 
            sourceImage.Clone(cropArea, sourceImage.PixelFormat);

如果源图像小于目标图像大小,这显然会失败,但你明白了。

答案 1 :(得分:1)

如果需要,此方法将保存在中心裁剪的图像:

bool SaveCroppedImage(Image image, int targetWidth, int targetHeight, string filePath)
{
    ImageCodecInfo jpgInfo = ImageCodecInfo.GetImageEncoders().Where(codecInfo => codecInfo.MimeType == "image/jpeg").First();
    Image finalImage = image;
    System.Drawing.Bitmap bitmap = null;
    try
    {
        int left = 0;
        int top = 0;
        int srcWidth = targetWidth;
        int srcHeight = targetHeight;
        bitmap = new System.Drawing.Bitmap(targetWidth, targetHeight);
        double croppedHeightToWidth = (double)targetHeight / targetWidth;
        double croppedWidthToHeight = (double)targetWidth / targetHeight;

        if (image.Width > image.Height)
        {
            srcWidth = (int)(Math.Round(image.Height * croppedWidthToHeight));
            if (srcWidth < image.Width)
            {
                srcHeight = image.Height;
                left = (image.Width - srcWidth) / 2;
            }
            else
            {
                srcHeight = (int)Math.Round(image.Height * ((double)image.Width / srcWidth));
                srcWidth = image.Width;
                top = (image.Height - srcHeight) / 2;
            }
        }
        else
        {
            srcHeight = (int)(Math.Round(image.Width * croppedHeightToWidth));
            if (srcHeight < image.Height)
            {
                srcWidth = image.Width;
                top = (image.Height - srcHeight) / 2;
            }
            else
            {
                srcWidth = (int)Math.Round(image.Width * ((double)image.Height / srcHeight));
                srcHeight = image.Height;
                left = (image.Width - srcWidth) / 2;
            }
        }
        using (Graphics g = Graphics.FromImage(bitmap))
        {
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.PixelOffsetMode = PixelOffsetMode.HighQuality;
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.DrawImage(image, new Rectangle(0, 0, bitmap.Width, bitmap.Height), new Rectangle(left, top, srcWidth, srcHeight), GraphicsUnit.Pixel);
        }
        finalImage = bitmap;
    }
    catch { }
    try
    {
        using (EncoderParameters encParams = new EncoderParameters(1))
        {
            encParams.Param[0] = new EncoderParameter(Encoder.Quality, (long)100);
            //quality should be in the range [0..100] .. 100 for max, 0 for min (0 best compression)
            finalImage.Save(filePath, jpgInfo, encParams);
            return true;
        }
    }
    catch { }
    if (bitmap != null)
    {
        bitmap.Dispose();
    }
    return false;
}

答案 2 :(得分:-1)

使用目标大小创建新的Bitmap对象。

围绕该位图创建图形对象。

在Graphcs对象上,使用适当的参数调用DrawImage(),并从第一张图片中剪切出正确的段。

代码将类似于:

Bitmap dstBitmap=new Bitmap(200, 200);
using (Graphics g=Graphics.FromImage(dstBitmap)) 
{
    srcBitmap.DrawImage(dstBitmap, /* cropping parameters here */);
}
//  at the end you'll have your bitmap in dstBitmap, ...

我没有包含方法的文字参数,使用intellisense和manual来计算它们。