Question

我需要从用户那里获得一张具有不同格式扩展名的图片，并且我希望始终将其保存为“jpg”，以便于处理。在没有武装质量的情况下，有没有一种好的方法可以做到这一点？

Answer 1

来自：http://msdn.microsoft.com/en-us/library/system.drawing.imaging.encoderparameter.aspx

private void VaryQualityLevel()
{
// Get a bitmap.
Bitmap bmp1 = new Bitmap(@"c:\TestPhoto.jpg");
ImageCodecInfo jpgEncoder = GetEncoder(ImageFormat.Jpeg);

// Create an Encoder object based on the GUID
// for the Quality parameter category.
System.Drawing.Imaging.Encoder myEncoder =
    System.Drawing.Imaging.Encoder.Quality;

// Create an EncoderParameters object.
// An EncoderParameters object has an array of EncoderParameter
// objects. In this case, there is only one
// EncoderParameter object in the array.
EncoderParameters myEncoderParameters = new EncoderParameters(1);

EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 
    50L);
myEncoderParameters.Param[0] = myEncoderParameter;
bmp1.Save(@"c:\TestPhotoQualityFifty.jpg", jpgEncoder, 
    myEncoderParameters);

myEncoderParameter = new EncoderParameter(myEncoder, 100L);
myEncoderParameters.Param[0] = myEncoderParameter;
bmp1.Save(@"c:\TestPhotoQualityHundred.jpg", jpgEncoder, 
    myEncoderParameters);

// Save the bitmap as a JPG file with zero quality level compression.
myEncoderParameter = new EncoderParameter(myEncoder, 0L);
myEncoderParameters.Param[0] = myEncoderParameter;
bmp1.Save(@"c:\TestPhotoQualityZero.jpg", jpgEncoder, 
    myEncoderParameters);

}

...

private ImageCodecInfo GetEncoder(ImageFormat format)
{

    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

    foreach (ImageCodecInfo codec in codecs)
    {
        if (codec.FormatID == format.Guid)
        {
            return codec;
        }
    }
    return null;
}

Answer 2

我使用这个简单的扩展来转换流，它所做的只是将其转换而不做任何质量。

public static Stream ConvertImage(this Stream originalStream, ImageFormat format)
{
                var image = Image.FromStream(originalStream);

                var stream = new MemoryStream();
                image.Save(stream, format);
                stream.Position = 0;
                return stream;
}

用法：

var outputStream = gifStream.ConvertImage(ImageFormat.Png);

Answer 3

Windows GDI +提供Image class和Bitmap class进行存储内存中的图像和内存中的图像处理。 GDI +写图像借助图像编码器到磁盘文件并加载图像借助图像解码器的磁盘文件。

检查Image.Save Method重载以实现您的功能。它支持ImageFormat Class类型的各种图像格式。

关注Image.Save Method (String, ImageCodecInfo, EncoderParameters)上的示例，该示例将允许您使用编码等保存Jpg文件。

代码段：

using System;
using System.Drawing;
using System.Drawing.Imaging;
class Example_SetJPEGQuality
{
    public static void Main()
    {
        Bitmap myBitmap;
        ImageCodecInfo myImageCodecInfo;
        Encoder myEncoder;
        EncoderParameter myEncoderParameter;
        EncoderParameters myEncoderParameters;

        // Create a Bitmap object based on a BMP file.
        myBitmap = new Bitmap("Shapes.bmp");

        // Get an ImageCodecInfo object that represents the JPEG codec.
        myImageCodecInfo = GetEncoderInfo("image/jpeg");

        // Create an Encoder object based on the GUID

        // for the Quality parameter category.
        myEncoder = Encoder.Quality;

        // Create an EncoderParameters object.

        // An EncoderParameters object has an array of EncoderParameter

        // objects. In this case, there is only one

        // EncoderParameter object in the array.
        myEncoderParameters = new EncoderParameters(1);

        // Save the bitmap as a JPEG file with quality level 25.
        myEncoderParameter = new EncoderParameter(myEncoder, 25L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes025.jpg", myImageCodecInfo, myEncoderParameters);

        // Save the bitmap as a JPEG file with quality level 50.
        myEncoderParameter = new EncoderParameter(myEncoder, 50L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes050.jpg", myImageCodecInfo, myEncoderParameters);

        // Save the bitmap as a JPEG file with quality level 75.
        myEncoderParameter = new EncoderParameter(myEncoder, 75L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes075.jpg", myImageCodecInfo, myEncoderParameters);
    }

//编解码器信息

  private static ImageCodecInfo GetEncoderInfo(String mimeType)
        {
            int j;
            ImageCodecInfo[] encoders;
            encoders = ImageCodecInfo.GetImageEncoders();
            for(j = 0; j < encoders.Length; ++j)
            {
                if(encoders[j].MimeType == mimeType)
                    return encoders[j];
            }
            return null;
        }

    }

希望这有帮助..

Answer 4

您可以使用Image API在内存中创建图像，然后将其保留在JPG中。 http://msdn.microsoft.com/en-us/library/ms142147.aspx

c＃将图像格式转换为jpg

4 个答案: