如何调整图像的大小 C# [英] How to resize an Image C#

问题描述

作为Size，Width 和Height 是System.Drawing 的Get() 属性.图片;
如何在 C# 中在运行时调整 Image 对象的大小?

As Size, Width and Height are Get() properties of System.Drawing.Image;
How can I resize an Image object at run-time in C#?

现在，我正在创建一个新的 Image 使用:

Right now, I am just creating a new Image using:

// objImage is the original Image
Bitmap objBitmap = new Bitmap(objImage, new Size(227, 171));

推荐答案

这将执行高质量的调整大小:

This will perform a high quality resize:

/// <summary>
/// Resize the image to the specified width and height.
/// </summary>
/// <param name="image">The image to resize.</param>
/// <param name="width">The width to resize to.</param>
/// <param name="height">The height to resize to.</param>
/// <returns>The resized image.</returns>
public static Bitmap ResizeImage(Image image, int width, int height)
{
    var destRect = new Rectangle(0, 0, width, height);
    var destImage = new Bitmap(width, height);

    destImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);

    using (var graphics = Graphics.FromImage(destImage))
    {
        graphics.CompositingMode = CompositingMode.SourceCopy;
        graphics.CompositingQuality = CompositingQuality.HighQuality;
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphics.SmoothingMode = SmoothingMode.HighQuality;
        graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

        using (var wrapMode = new ImageAttributes())
        {
            wrapMode.SetWrapMode(WrapMode.TileFlipXY);
            graphics.DrawImage(image, destRect, 0, 0, image.Width,image.Height, GraphicsUnit.Pixel, wrapMode);
        }
    }

    return destImage;
}

• wrapMode.SetWrapMode(WrapMode).TileFlipXY) 防止图像边界周围出现重影——简单的调整大小会采样超出图像边界的透明像素，但通过镜像我们可以获得更好的样本(这个设置非常明显)
• destImage.SetResolution 不论物理尺寸如何都保持 DPI -- 在缩小图像尺寸或打印时可能会提高质量
• 合成控制像素与背景的混合方式 -- 可能不需要，因为我们只绘制一件事.
  • graphics.CompositingMode 确定来自源图像的像素是覆盖还是与背景像素组合.SourceCopy 指定在呈现颜色时，它会覆盖背景颜色.
  • graphics.CompositingQuality 决定了分层图像的渲染质量级别.

  保持纵横比留给读者作为练习(实际上，我只是不认为这个功能的工作是为你做这件事).

  Maintaining aspect ratio is left as an exercise for the reader (actually, I just don't think it's this function's job to do that for you).

  此外，这是一篇很好的文章，描述了一些调整图像大小的陷阱.上面的函数会覆盖大部分，但是你还是要担心保存.

  Also, this is a good article describing some of the pitfalls with image resizing. The above function will cover most of them, but you still have to worry about saving.

  这篇关于如何调整图像的大小 C#的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！