如何使用字节数组比较两个图像

I want to be able to convert from Byte[] to Image and vice versa.

我希望能够从Byte []转换为Image，反之亦然。

I've this two methods from here:

我从这里开始这两种方法：

public byte[] imageToByteArray(System.Drawing.Image imageIn)
{
    MemoryStream ms = new MemoryStream();
    imageIn.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
    return  ms.ToArray();
}

public Image byteArrayToImage(byte[] byteArrayIn)
{
     MemoryStream ms = new MemoryStream(byteArrayIn);
     Image returnImage = Image.FromStream(ms);
     return returnImage;
}

They seem to work, but if I do:

他们似乎工作，但如果我这样做：

byte[] pic = GetImageFromDb();
bool result = pic == imageToByteArray(byteArrayToImage(pic));

I get result = false!

我得到result = false！

Any way to correct this methods or some different functions to achieve my goal?

有没有办法纠正这种方法或一些不同的功能来实现我的目标？

Thanks!

谢谢！

4 个解决方案

#1

Using == will compare the object references if not overridden.

如果不重写，使用==将比较对象引用。

Since these are two different byte[] objects, the references are different.

由于这些是两个不同的byte []对象，因此引用是不同的。

You need to compare the byte[] objects item by item in order to confirm that they are identical. You can use SequenceEquals in this case.

您需要逐项比较byte []对象，以确认它们是相同的。在这种情况下，您可以使用SequenceEquals。

#2

== means that you have a reference to the same object in memory.

==表示您对内存中的同一对象有引用。

This shows how to compare byte arrays in a few different ways.

这显示了如何以几种不同的方式比较字节数组。

#3

I recently needed to write an image cropper that needed to save the fileBytes as an image. here is what I did. Hopefully this will help you.

我最近需要编写一个图像裁剪器，需要将fileBytes保存为图像。这就是我做的。希望这会对你有所帮助。

public Image byteArrayToImage(byte[] fileBytes)
{
    using (MemoryStream fileStream = new MemoryStream(fileBytes))
    {
        return Image.FromStream( fileStream );
    }
}

obviously my code for the cropping/saving expands upon this. But I was able to return an Image object from the file bytes.

很明显，我的裁剪/保存代码扩展到了这一点。但我能够从文件字节返回一个Image对象。

#4

When you re-encode an image, the resulting file (or byte array) can be (slightly?) different from the original version. Especially if what you retrieve from the database was a jpeg file!

重新编码图像时，生成的文件（或字节数组）可能（稍微？）与原始版本不同。特别是如果你从数据库中检索到的是一个jpeg文件！

So even if you compare the bytes in the arrays (instead of references) you can get differences.

因此，即使您比较数组中的字节（而不是引用），您也可以获得差异。

EDIT
When you read a byte[] (containing a GIF encoded image) into a BitMap, those bytes are decompressed into 4 (ARGB) bytes per pixel. When you save that BitMap to a (new) gif file (or byte[]), the newly encoded file could be different (for instance, the order in which the colors are stored). So there is no guarantee that the new file (or byte[]) is identical to the old one, although the image itself isn't changed.

编辑当您将一个字节[]（包含GIF编码图像）读入BitMap时，这些字节将被解压缩为每个像素4个（ARGB）字节。将BitMap保存到（新）gif文件（或byte []）时，新编码的文件可能不同（例如，存储颜色的顺序）。因此，无法保证新文件（或byte []）与旧文件相同，尽管图像本身不会更改。

#1