我必须压缩PNG文件图像，而不损失质量
本文关键字：损失 图像 压缩 PNG 文件 | 更新日期: 2023-09-27 18:12:01
我想压缩一个PNG图像，以减少其大小，但质量应保持不变。我试过压缩JPEG图片。图片压缩约90%，质量保持不变，但当我用它压缩PNG图像。没有结果，就没有压缩。相同的大小。
这是我的代码。public const string _StatusLog = "StatusLog.csv";
static void Main(string[] args)
{
Console.WriteLine(" ### WELCOME ###");
Console.Write("'n'nPlease enter image folder path :");
string imagePath = Console.ReadLine();
Program p = new Program();
p.VaryQualityLevel(imagePath);
Console.ReadLine();
}
private void VaryQualityLevel(string pathOfImage)
{
try
{
//Console.Write("Target Directory Path :");
string targetDirectory = pathOfImage;//Console.ReadLine();
if (targetDirectory != null)
{
string[] allDirectoryInTargetDirectory = Directory.GetDirectories(targetDirectory);
//PRODUCT DIRECOTY OPEN
Console.Write("Total Folders found = " + allDirectoryInTargetDirectory.Count());
Console.Read();
if (allDirectoryInTargetDirectory.Any())
{
foreach (var directory in allDirectoryInTargetDirectory)
{
string[] subDirectory = Directory.GetDirectories(directory); // ATTRIBUTE DIRECTORY OPEN
if (subDirectory.Any())
{
foreach (var filesInSubDir in subDirectory)
{
string[] allFilesInSubDir = Directory.GetFiles(filesInSubDir);
//FILES IN SUB DIR OPEN
if (allFilesInSubDir.Any())
{
foreach (var imageFile in allFilesInSubDir)
{
try
{
Bitmap bmp1 = new Bitmap(imageFile);//pathOfImage);
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.
#region SAVING THE COMPRESS IMAGE FILE
EncoderParameters myEncoderParameters = new EncoderParameters(1);
EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 50L);
myEncoderParameters.Param[0] = myEncoderParameter;
bmp1.Save(filesInSubDir + "''" + "Zip" + GettingImageNameForOptimizedImage(imageFile), jpgEncoder, myEncoderParameters);//pathOfImage
Console.WriteLine(filesInSubDir + GettingImageNameForOptimizedImage(imageFile) + " CREATED");//pathOfImage
#endregion
#region DELETING THE ORIGNAL FILE
bmp1.Dispose();
System.IO.File.Delete(filesInSubDir + "''" + GettingImageNameForOptimizedImage(imageFile));//pathOfImage
Console.WriteLine(imageFile.Replace("jpg", "png") + " DELETED");//pathOfImage
#endregion
//myEncoderParameter = new EncoderParameter(myEncoder, 100L);
//myEncoderParameters.Param[0] = myEncoderParameter;
//bmp1.Save("D:''" + RemovingImageFormat[0] + "100L" + ".jpg", jpgEncoder, myEncoderParameters);
#region BACK RENAMING FILE TO ORIGNAL NAME
System.IO.File.Move(filesInSubDir + "''" + "Zip" + GettingImageNameForOptimizedImage(imageFile), filesInSubDir + "''" + GettingImageNameForOptimizedImage(imageFile));
#endregion
}
catch (Exception ex)
{
Console.Write("'n" + ex.Message + " Press enter to continue :");
Console.ReadLine();
Console.Write("'nWould you like to retry ? [Y/N] :");
string resp = Console.ReadLine();
if (resp == "Y" || resp == "y")
{
Console.WriteLine(" -------------------'n'n");
Main(null);
}
}
}
}
}
}
}
}
}
}
catch (Exception ex)
{
Console.Write(ex);
Console.Read();
}
Console.Write("Press any key to exit...");
Console.Read();
// Get a bitmap. ###################################################################
}
private ImageCodecInfo GetEncoder(ImageFormat format)
{
ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
foreach (ImageCodecInfo codec in codecs)
{
if (codec.FormatID == format.Guid)
{
return codec;
}
}
return null;
}
public string GettingImageNameForOptimizedImage(string pathOfImage)
{
try
{
string[] splitingPathOfImage = pathOfImage.Split('''');
string[] RemovingImageFormat = splitingPathOfImage[splitingPathOfImage.Count() - 1].ToString().Split('.');
return RemovingImageFormat[0] + ".jpg";
}
catch (Exception)
{
return null;
}
return null;
}
public static void LoggingOperations(string ImageName, string Status, bool UpdateRequired)
{
try
{
if (!File.Exists(_StatusLog))
{
using (File.Create(_StatusLog)) { }
DirectorySecurity sec = Directory.GetAccessControl(_StatusLog);
SecurityIdentifier everyone = new SecurityIdentifier(WellKnownSidType.WorldSid, null);
sec.AddAccessRule(new FileSystemAccessRule(everyone, FileSystemRights.Modify | FileSystemRights.Synchronize, InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit, PropagationFlags.None, AccessControlType.Allow));
Directory.SetAccessControl(_StatusLog, sec);
}
if (UpdateRequired == true)
{
string UpdateStatusText = File.ReadAllText(_StatusLog);
UpdateStatusText = UpdateStatusText.Replace(ImageName, ImageName + "," + Status);
File.WriteAllText(_StatusLog, UpdateStatusText);
UpdateStatusText = "";
}
else
{
File.AppendAllText(_StatusLog, Environment.NewLine);
File.AppendAllText(_StatusLog, Status);
}
}
catch (Exception)
{
}
}
对于PNG压缩，我更改了以下行。
Bitmap bmp1 = new Bitmap(imageFile);//pathOfImage);
ImageCodecInfo jpgEncoder = GetEncoder(ImageFormat.Png);
PNG图像默认为32位。您可以将它们转换为8位:生成的文件将比原始文件小约5倍。对于大多数图像，质量的损失几乎是看不见的。
这就是在线png压缩器所做的。
你可以自己使用nQuant: http://nquant.codeplex.com/(在Nuget上可用)
var quantizer = new WuQuantizer();
using(var quantized = quantizer.QuantizeImage(bmp1))
{
quantized.Save(targetPath, ImageFormat.Png);
}
该方法的完整解释可在此博客文章http://www.hurryupandwait.io/blog/convert-32-bit-pngs-to-high-quality-8-bit-pngs-with-c
我还建议看看imagessharp，它也可以与。net Core一起使用
using (var image = Image.Load(fileData)) // fileData could be file path or byte array etc.
{
var h = image.Size().Height / 2;
var w = image.Size().Width / 2;
var options = new ResizeOptions
{
Mode = ResizeMode.Stretch,
Size = new Size(w, h)
};
image.Mutate(_ => _.Resize(options));
using (var destStream = new MemoryStream())
{
var encoder = new JpegEncoder();
image.Save(destStream, encoder);
// Do something with output stream
}
}
PNG压缩的一个主要变量是压缩速度和输出大小之间的权衡。PNG压缩实际上可能相当慢，因为它涉及到搜索数据缓冲区以匹配模式。您可以通过限制编码器搜索缓冲区的大小来加快压缩速度。
你的编码器应该有一个设置，允许你指定如何搜索匹配。
如果您的输入PNG图像没有使用编码器搜索整个缓冲区进行压缩，那么您可以通过在应用程序中搜索整个缓冲区来获得一些改进的压缩。但是，您不太可能获得重大改进。
在像素大小和颜色深度一致的情况下，PNG应该是无损的。
https://pnggauntlet.com/