EmguCV - 保存图像时如何指定jpeg质量？

Question

我使用以下C#EmguCV代码保存jpeg图像:

Emgu.CV.Image<Gray, byte> image
...
image.Save("imageName.jpg");

但是图像以极低的质量存储(每8x8像素1个颜色的正方形).

当我保存bmp时一切都还可以:

Emgu.CV.Image<Gray, byte> image
...
image.Save("imageName.bmp");

如何在使用时增加jpeg质量Emgu.Cv.Image.Save或者我应该调用其他功能？为什么默认质量如此之低？

试图询问EmguCV论坛,但它无法访问.

Answer 1

EMGU只有image.Save(filename)因此你必须使用保存图像的.Net方法.此代码源自此处.我将代码分开以便于此代码打开文件然后尝试保存它.这是你对saveJpeg感兴趣的函数(SaveFile.FileName,img.ToBitmap(),100); .基于函数saveJpeg(字符串路径,位图img,长质量).

open.Filter = "Image Files (*.tif; *.dcm; *.jpg; *.jpeg; *.bmp)|*.tif; *.dcm; *.jpg; *.jpeg; *.bmp";
if (open.ShowDialog() == DialogResult.OK)
{
    Image<Bgr, Byte> img = new Image<Bgr, Byte>(open.FileName);
    SaveFileDialog SaveFile = new SaveFileDialog();
    if (SaveFile.ShowDialog() == DialogResult.OK)
    {
        saveJpeg(SaveFile.FileName, img.ToBitmap(), 100);
    }
}

现在,为了获得该函数的代码,您可以将以下内容复制并粘贴到项目中,不要忘记代码顶部的using语句.

using System.Drawing.Imaging;

private void saveJpeg(string path, Bitmap img, long quality)
{
    // Encoder parameter for image quality

    EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);

    // Jpeg image codec
    ImageCodecInfo jpegCodec = this.getEncoderInfo("image/jpeg");

    if (jpegCodec == null)
    return;

    EncoderParameters encoderParams = new EncoderParameters(1);
    encoderParams.Param[0] = qualityParam;

    img.Save(path, jpegCodec, encoderParams);
}

private ImageCodecInfo getEncoderInfo(string mimeType)
{
    // Get image codecs for all image formats
    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();

    // Find the correct image codec
    for (int i = 0; i < codecs.Length; i++)
    if (codecs[i].MimeType == mimeType)
    return codecs[i];
    return null;
}

如果你遇到困难,这是EMGU最好的方法让我知道.

希望这可以帮助,

克里斯

Answer 2

如果有人对此感兴趣，则基于 Chris 的回答是一个简单的扩展；

using System;
using System.Linq;
using System.Drawing.Imaging;
using Emgu.CV.Structure;

public static class EmguImageSave
{
    /// <summary>
    /// Save a jpeg image with a specified quality
    /// </summary>
    /// <param name="path">Name of the file to which to save the image</param>
    /// <param name="quality">Byte that specifies JPEG Quality of the image encoder</param>
    public static void Save( this Emgu.CV.Image<Bgr, Byte> img, string filename, double quality )
    {
        var encoderParams = new EncoderParameters( 1 );
        encoderParams.Param[0] = new EncoderParameter(
            System.Drawing.Imaging.Encoder.Quality,
            (long)quality
            );

        var jpegCodec = (from codec in ImageCodecInfo.GetImageEncoders()
                         where codec.MimeType == "image/jpeg"
                         select codec).Single();

        img.Bitmap.Save( filename, jpegCodec, encoderParams );
    }
}

用法;

var fname = 0;
while( true )
{
    try
    {
        var img = capture.QueryFrame();
        img.Save( String.Format( @"c:\rec\{0}.jpg", ++fname), 100 );
    } catch( Exception ) { break; }
}