// Create image.
Image image1 = Image.FromFile("c:\\Photo1.jpg");
// Get a PropertyItem from image1. Because PropertyItem does not
// have public constructor, you first need to get existing PropertyItem
PropertyItem propItem = image1.GetPropertyItem(20624);
// Change the ID of the PropertyItem.
propItem.Id = 20625;
// Set the new PropertyItem for image1.
image1.SetPropertyItem(propItem);
// Save the image.
image1.Save("c:\\Photo1.jpg", ImageFormat.Jpg);
// Create image.
Image image1 = Image.FromFile("c:\\Photo1.jpg");
// Get a PropertyItem from image1. Because PropertyItem does not
// have public constructor, you first need to get existing PropertyItem
PropertyItem propItem = image1.GetPropertyItem(20624);
// Change the ID of the PropertyItem.
propItem.Id = 20625;
// Set the new PropertyItem for image1.
image1.SetPropertyItem(propItem);
// Save the image.
image1.Save("c:\\Photo1.jpg", ImageFormat.Jpg);
List of all possible PropertyItem ids (including exif) you can found here.
Update: Agreed, this method will re-encode image on save. But I have remembered another method, in WinXP SP2 and later there is new imaging components added - WIC, and you can use them to lossless write metadate - How-to: Re-encode a JPEG Image with Metadata.
private void LosslessJpegTest() {
var original = "d:\\!test\\TestInTest\\20150205_123011.jpg";
var copy = original;
const BitmapCreateOptions createOptions = BitmapCreateOptions.PreservePixelFormat | BitmapCreateOptions.IgnoreColorProfile;
for (int i = 0; i < 100; i++) {
using (Stream originalFileStream = File.Open(copy, FileMode.Open, FileAccess.Read)) {
BitmapDecoder decoder = BitmapDecoder.Create(originalFileStream, createOptions, BitmapCacheOption.None);
if (decoder.CodecInfo == null || !decoder.CodecInfo.FileExtensions.Contains("jpg") || decoder.Frames[0] == null)
continue;
BitmapMetadata metadata = decoder.Frames[0].Metadata == null
? new BitmapMetadata("jpg")
: decoder.Frames[0].Metadata.Clone() as BitmapMetadata;
if (metadata == null) continue;
var keywords = metadata.Keywords == null ? new List<string>() : new List<string>(metadata.Keywords);
keywords.Add($"Keyword {i:000}");
metadata.Keywords = new ReadOnlyCollection<string>(keywords);
JpegBitmapEncoder encoder = new JpegBitmapEncoder {QualityLevel = 80};
encoder.Frames.Add(BitmapFrame.Create(decoder.Frames[0], decoder.Frames[0].Thumbnail, metadata,
decoder.Frames[0].ColorContexts));
copy = original.Replace(".", $"_{i:000}.");
using (Stream newFileStream = File.Open(copy, FileMode.Create, FileAccess.ReadWrite)) {
encoder.Save(newFileStream);
}
}
}
}
I wrote a small test where I compress one file many times to see the quality degradation and you can see it in the third-fourth compression, which is very bad.
But luckily, if you always use same QualityLevel with JpegBitmapEncoder there is no degradation.
In this example I rewrite keywords 100x in metadata and the quality seems not to change.
private void LosslessJpegTest() {
var original = "d:\\!test\\TestInTest\\20150205_123011.jpg";
var copy = original;
const BitmapCreateOptions createOptions = BitmapCreateOptions.PreservePixelFormat | BitmapCreateOptions.IgnoreColorProfile;
for (int i = 0; i < 100; i++) {
using (Stream originalFileStream = File.Open(copy, FileMode.Open, FileAccess.Read)) {
BitmapDecoder decoder = BitmapDecoder.Create(originalFileStream, createOptions, BitmapCacheOption.None);
if (decoder.CodecInfo == null || !decoder.CodecInfo.FileExtensions.Contains("jpg") || decoder.Frames[0] == null)
continue;
BitmapMetadata metadata = decoder.Frames[0].Metadata == null
? new BitmapMetadata("jpg")
: decoder.Frames[0].Metadata.Clone() as BitmapMetadata;
if (metadata == null) continue;
var keywords = metadata.Keywords == null ? new List<string>() : new List<string>(metadata.Keywords);
keywords.Add($"Keyword {i:000}");
metadata.Keywords = new ReadOnlyCollection<string>(keywords);
JpegBitmapEncoder encoder = new JpegBitmapEncoder {QualityLevel = 80};
encoder.Frames.Add(BitmapFrame.Create(decoder.Frames[0], decoder.Frames[0].Thumbnail, metadata,
decoder.Frames[0].ColorContexts));
copy = original.Replace(".", $"_{i:000}.");
using (Stream newFileStream = File.Open(copy, FileMode.Create, FileAccess.ReadWrite)) {
encoder.Save(newFileStream);
}
}
}
}
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评论（4）
如果您计划编写自己的库来编辑标签，则以下是 Exif 交换格式的规范。
http://www.exif.org/specifications.html
这是一个用 Perl 编写的库，满足您可以从中了解您的需求：
http://www.sno。 phy.queensu.ca/~phil/exiftool/
这是一个不错的 .NET 库，用于 Exif 评估，来自 代码项目：
http://www.codeproject.com/KB/graphics /exiftagcol.aspx
Here are the specifications for the Exif interchange format, if you plan to code your own library for editing tags.
http://www.exif.org/specifications.html
Here's a library written in Perl that meets your needs that you may be able to learn from:
http://www.sno.phy.queensu.ca/~phil/exiftool/
Here's a decent .NET library for Exif evaluation from The Code Project:
http://www.codeproject.com/KB/graphics/exiftagcol.aspx
您可以在没有任何外部库的情况下执行此操作：
您可以找到的所有可能的 PropertyItem id（包括 exif）的列表 此处。
更新：同意，此方法将在保存时重新编码图像。 但我想起了另一种方法，在WinXP SP2及更高版本中添加了新的成像组件-WIC，你可以使用它们无损写入元数据-操作方法：使用元数据重新编码 JPEG 图像。
You can do this without any external lib:
List of all possible PropertyItem ids (including exif) you can found here.
Update: Agreed, this method will re-encode image on save. But I have remembered another method, in WinXP SP2 and later there is new imaging components added - WIC, and you can use them to lossless write metadate - How-to: Re-encode a JPEG Image with Metadata.
exiv2net 库（exiv2 之上的 .NET 包装器）可能就是您想要的为了。
exiv2net library (a .NET wrapper on top of exiv2) may be what you're looking for.
我写了一个小测试，我多次压缩一个文件来查看质量下降情况，你可以在第三次第四次压缩中看到它，这是非常糟糕的。
但幸运的是，如果您始终对 JpegBitmapEncoder 使用相同的 QualityLevel，则不会出现降级。
在此示例中，我在元数据中重写了 100 倍的关键字，但质量似乎没有改变。
I wrote a small test where I compress one file many times to see the quality degradation and you can see it in the third-fourth compression, which is very bad.
But luckily, if you always use same QualityLevel with JpegBitmapEncoder there is no degradation.
In this example I rewrite keywords 100x in metadata and the quality seems not to change.