c＃将图像格式转换为jpg
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，在c＃中有一个很好的方法吗？
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 jgpEncoder = 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", jgpEncoder, myEncoderParameters); myEncoderParameter = new EncoderParameter(myEncoder, 100L); myEncoderParameters.Param[0] = myEncoderParameter; bmp1.Save(@"c:\TestPhotoQualityHundred.jpg", jgpEncoder, 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", jgpEncoder, myEncoderParameters); } ... private ImageCodecInfo GetEncoder(ImageFormat format) { ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders(); foreach (ImageCodecInfo codec in codecs) { if (codec.FormatID == format.Guid) { return codec; } } return null; } 我使用这个简单的扩展来转换流，它所做的只是转换它，并没有做任何质量。
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);
Windows GDI +提供了Image类和Bitmap类 ，用于在内存中存储图像和操作内存中的图像。 GDI +借助图像编码器将图像写入磁盘文件，并在图像解码器的帮助下加载磁盘文件中的图像。
检查Image.Save方法重载以实现您的function。 它支持ImageFormat类型的各种图像格式。
按照Image.Save方法（String，ImageCodecInfo，EncoderParameters）上的示例，它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..
试试这个：
public static class BitmapExtension { public static void Save(this Bitmap bitmap, String fileName, ImageFormat imageFormat, long quality = 75L) { using (var encoderParameters = new EncoderParameters(1)) using (encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality)) { ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders(); bitmap.Save(fileName, codecs.Single(codec => codec.FormatID == imageFormat.Guid), encoderParameters); } } } ... Bitmap bitmap = new Bitmap("myImage.bmp"); bitmap.Save("myImage.jpg", ImageFormat.Jpeg, 50L);
您可以使用Image API在内存中创建映像，然后将其保留在JPG中。 http://msdn.microsoft.com/en-us/library/ms142147.aspx