• 对于照片一般采用无损压缩方法： 【1】行程长度压缩： 计算机中每个图片都包括很多像素的图像，这些像素而言比较密集并且比较单一，所以我们为了节省存储空间，将其中相同的像素采用单一的方式或者只填充一个像素...
对于照片一般采用无损压缩方法：
【1】行程长度压缩：
计算机中每个图片都包括很多像素的图像，这些像素而言比较密集并且比较单一，所以我们为了节省存储空间，将其中相同的像素采用单一的方式或者只填充一个像素来达到压缩的目的；
【2】增量调制压缩：
这种方式是利用了像素的相邻性特点来压缩，像素相邻比较密集，所以利用相邻来达到压缩的目的从而节省空间；
【3】霍夫曼表压缩：
计算出每个像素的画面的概率值，然后利用频繁出现的编码用最小的概率值达到节省空间的目的


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• 摘要:C#源码,文件操作,无损压缩　C# 普通压缩图片和无损压缩图片两种不同源码示例，无损压缩当然比较好了，源码可正确编译，其中无损压缩图片的程序界面请参见截图。Compositing文件夹中的为普通的图片压缩程序实例...
• PNG无损压缩
• 图像有损压缩与无损压缩Lossy and lossless compression are two kinds of data compression techniques. Here in this article, you will get to learn about what is lossy and lossless compression, their ...
图像有损压缩与无损压缩Lossy and lossless compression are two kinds of data compression techniques. Here in this article, you will get to learn about what is lossy and lossless compression, their differences, and uses.
有损和无损压缩是两种数据压缩技术。 在本文的此处，您将了解什么是有损和无损压缩，它们的区别和用途。
因此，让我们从基础开始。
什么是数据压缩？ (What is Data Compression?)
Data compression is the process of diminishing the storage size of any data or file so that it consumes less space on the disk. It is the technique of modifying, restructuring, encoding and converting the schema or instance of any data to reduce its size.
数据压缩是减小任何数据或文件的存储大小，以使其在磁盘上占用较少空间的过程。 它是一种修改，重组，编码和转换任何数据的模式或实例以减小其大小的技术。
In simple words, it is converting the file in such a way that its size is reduced to a maximum extent. Data compressions is also known as bit-rate reduction or source coding.
简而言之，它将以最大程度减小文件大小的方式转换文件。 数据压缩也称为比特率降低或源编码。
Check the diagram below:
检查下图：
An example of an image that is converted or compressed to reduce its size without losing the ability to reconstruct the image.
转换或压缩以减小其尺寸而又不损失重建图像能力的图像的示例。
Now, the question here is why there is a need for data compression?
现在，这里的问题是为什么需要数据压缩？
There are two primary reasons for the same.
造成这种情况的主要原因有两个。
Storage – it helps in reducing the size of data that is required to store it on the disk 存储–它有助于减少将数据存储在磁盘上所需的数据量 Time – saves time in data transmission as the size is reduced to an extent 时间–尺寸减小到一定程度，节省了数据传输时间 You are getting the point!
您明白了！
Now coming back to the main topic, there are mainly two types of data compression techniques. Let’s discuss them.
现在回到主要主题，主要有两种类型的数据压缩技术。 让我们讨论一下。
数据压缩技术 (Data Compression Techniques)
有损压缩 (Lossy Compression)
Lossy compression is a technique that involves the elimination of a specific amount of data. It helps in reducing the file size to a great extent without any noticeable thing. Also, once the file is compressed, it cannot be restored back to its original form as the data from the file is significantly reduced. This technique is much more useful when the quality of the file is not essential. Additionally, it helps to save much space on the disk to store the data.
有损压缩是一种涉及消除特定数量数据的技术。 它有助于在没有任何明显注意的情况下大大减小文件大小。 同样，一旦压缩了文件，由于来自文件的数据将大大减少，因此无法将其恢复为原始格式。 当文件的质量不是很重要时，此技术会更加有用。 此外，它有助于节省磁盘上的大量空间来存储数据。
Lossy compression is not useful when the quality of the file is essential. Besides, if there’s any further analysis to be processed on the record, this method is not ideal. This method is generally used for audio and video compression, where there is a significant amount of data loss, and even users cannot recognize it.
当文件的质量至关重要时，有损压缩是没有用的。 此外，如果记录上有任何进一步的分析要处理，这种方法也不理想。 此方法通常用于音频和视频压缩，这会导致大量数据丢失，甚至用户也无法识别它。
Example of lossy compression: JPEG image
有损压缩的示例：JPEG图像
Image Source
图片来源
“Compressed image (left) shows blocking artifacts compared to the original image (right) as a result of the JPEG compression scheme used.”
“由于使用了JPEG压缩方案，与原始图像(右)相比，压缩图像(左)显示出块状伪影。”
无损压缩 (Lossless Compression)
Lossless compression is a technique that involves only a certain amount of elimination of data. This technique also helps in reducing the file size, but not to the greater extent as that of lossy compression. Instead, in this method, if the file is compressed, it can be restored back to its original form. Further, the quality of the data is not compromised; hence, the reduction in size is not much.
无损压缩是一种仅涉及消除一定量数据的技术。 此技术还有助于减小文件大小，但不会像有损压缩那样在很大程度上。 相反，在这种方法中，如果文件被压缩，则可以将其还原回其原始形式。 此外，数据的质量不会受到影响； 因此，尺寸减小不多。
Lossless compression is not useful when you want reduced size for extra storage. Also, if there is any further analysis to be performed on the file, lossless compression is not beneficial. It is useful for maintaing the originality of files by eliminating only unwanted data. This technique is commonly used for text files, sensitive documents, and confidential information.
当您希望减小尺寸以增加存储空间时，无损压缩将无用。 此外，如果要对文件执行任何进一步的分析，则无损压缩将无益。 通过仅消除不需要的数据，对于保持文件的原始性很有用。 此技术通常用于文本文件，敏感文档和机密信息。
Example of lossless compression: PNG image
无损压缩示例：PNG图像
Image Source
图片来源
“The original image (left) is identical to the compressed image (right). It is represented by the identical graphs at the bottom that show the grey values for the pixels in each column is the same between the two images.”
“原始图像(左)与压缩图像(右)相同。 它由底部的相同图形表示，该图形显示两列图像中每列像素的灰度值相同。”
有损压缩与无损压缩之间的区别 (Difference between Lossy and Lossless Compression)

Basis
Lossy Compression
Lossless Compression

Definition
Lossy compression is a technique that involves the elimination of a specific amount of data. It helps in reducing the file size to a great extent without any noticeable thing
Lossless compression is a technique that involves only a certain amount of elimination of data. This technique also helps in reducing the file size, but not to the greater extent

Compression Ratio
High
Low

File Quality
Low
High

Elimination of Data
Even the necessary data is also removed which isn’t noticeable
Only some specific amount of unwanted data is removed

Restoration
Cannot restore its original form
Can restore its original form

Loss of Information
This technique involves some loss of information
This technique doesn’t include any loss of information

Data Accommodation
More data accommodation
Less data accommodation

Distortion
Files are distorted
No distortion

Data holding capacity
More
Less

Algorithms Used
Transform coding, DCT, DWT, fractal compression, RSSMS
RLW, LZW, Arithmetic encoding, Huffman encoding, Shannon Fano coding

File Types
JPEG, GIF, MP3, MP4, MKV, OGG, etc.
RAW, BMP, PNG, WAV, FLAC, ALAC, etc.

基础
有损压缩
无损压缩

定义
有损压缩是一种涉及消除特定数量数据的技术。 它有助于在没有任何明显注意的情况下大大减小文件大小
无损压缩是一种仅涉及消除一定量数据的技术。 此技术还有助于减小文件大小，但不会在更大程度上

压缩率
高
低

档案品质
低
高

消除数据
即使必要的数据也被删除，这并不明显
仅删除了特定数量的有害数据

恢复
无法恢复其原始形式
可以恢复其原始形式

信息丢失
此技术涉及一些信息丢失
此技术不包括任何信息丢失

数据调整
更多数据住宿
数据容纳量减少

失真
文件变形
无失真

资料储存能力
更多
减

使用的算法
RLW，LZW，算术编码，霍夫曼编码，香农法诺编码

文件类型
JPEG，GIF，MP3，MP4，MKV，OGG等
RAW，BMP，PNG，WAV，FLAC，ALAC等

使用哪个？ (Which One to Use?)
Although both are the types of data compression, each can be useful under different situations. Like, lossy compression helps in reducing the file size, which means it is helpful to those who have vast amounts of data stored on the database. So, this technique is useful in storing the data with a much-diminished size. Also, for webpages files of such lower size is beneficial for faster loading.
尽管这两种都是数据压缩的类型，但是每种压缩在不同情况下都是有用的。 像，有损压缩有助于减小文件大小，这对那些在数据库上存储大量数据的用户有帮助。 因此，此技术在存储大小减小的数据时很有用。 同样，对于网页而言，这种较小的文件有利于更快地加载。
Further, this process doesn’t allow any after analysis of the data once the compression is completed. Also, the file cannot be restructured in its original form as it involves the loss of data.
此外，压缩完成后，此过程将不允许对数据进行任何后续分析。 同样，该文件不能以其原始形式进行重组，因为它涉及数据丢失。
Unlike lossy compression, lossless compression doesn’t involve any loss of data. Neither the quality of data is compromised, nor the size of data is excessively reduced. It keeps the original format so it can be restored, and further operation can be performed. This method is helpful for those who need to access the data back again without compromising its quality.
与有损压缩不同，无损压缩不涉及任何数据丢失。 既不会损害数据质量，也不会过度减少数据大小。 它保留了原始格式，因此可以还原，并且可以执行进一步的操作。 此方法对需要再次访问数据而不影响其质量的用户很有用。
最后的话 (Final Words)
Both lossy compression and lossless compression helps in the compression of data in their unique way. While lossy compression is useful to store data by compromising the data, lossless compression doesn’t. Lossless compression technique is beneficial for maintaing the originality of data, and lossy compression, on the other hand, doesn’t. Both the methods are helpful in database management, to identify and compress files accordingly.
有损压缩和无损压缩都以其独特的方式帮助压缩数据。 尽管有损压缩通过破坏数据来存储数据很有用，但无损压缩却没有。 无损压缩技术有利于保持数据的原始性，而无损压缩则不能。 两种方法都有助于数据库管理，从而相应地识别和压缩文件。
If there’s any other query regarding data compression or both the techniques of data compression, then let us know in the comment box below.
如果还有关于数据压缩或这两种数据压缩技术的任何其他查询，请在下面的注释框中告知我们。
翻译自: https://www.thecrazyprogrammer.com/2019/12/lossy-and-lossless-compression.html图像有损压缩与无损压缩
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• 图片 无损 压缩 软件 mac_ImageOptim.zip 图片 无损 压缩
• 照片无损压缩软件能将一个文件夹下所有图片进行同时压缩，可以按百分比进行压缩，也可指定图片的宽和高进行压缩，可以生成缩略图。 菜单功能： 1、选择图片所在路径 2、选择将图片保存到指定文件夹 3、缩略图设置：...
• 图像有损压缩与无损压缩Modern web browsers accept four image formats by default: JPEG, GIF, PNG and SVG. But before talking about formats, let’s introduce two extremely important terms: lossless and ...
图像有损压缩与无损压缩Modern web browsers accept four image formats by default: JPEG, GIF, PNG and SVG. But before talking about formats, let’s introduce two extremely important terms: lossless and lossy compression.
现代网络浏览器默认接受四种图像格式： JPEG ， GIF ， PNG和SVG 。 但是在讨论格式之前，我们先介绍两个非常重要的术语： 无损压缩和有损压缩。
Almost all images are compressed in some way. That is, the raw binary data that makes up the individual pixels and their color is packaged up and rearranged to achieve the smallest file size possible for any particular format. There are many different methods of data compression, but every system comes down to one simple question: whether it physically changes the data in the image. 几乎所有图像都以某种方式压缩。 即，构成单个像素及其颜色的原始二进制数据被打包并重新排列，以实现任何特定格式可能的最小文件大小。 数据压缩有很多不同的方法，但是每个系统都可以解决一个简单的问题：它是否物理地更改了图像中的数据。
Lossless compression does not change bits. It rearranges them, and tries to pack them into a smaller space - think of different arrangements of boxes in a moving van in an attempt to fit more inside - but does not physically change them. You obviously want a lossless compression scheme in situations for which fidelity to the original data is paramount. .zip is a ubiquitous compression scheme: bits go in, information is re-arranged and compressed, but the same bits come out after you uncompress the .zip. (You don't want the “Z’s” in a compressed Microsoft Word document to be changed to “k’s” just because it would make the file smaller.) 无损压缩不会更改位。 它会重新排列它们，并尝试将它们包装在较小的空间中-考虑在移动的货车中尝试不同的盒子布​​置，以试图容纳更多的内部空间-但不会在物理上改变它们。 在原始数据的保真度至关重要的情况下，您显然希望使用无损压缩方案。 .zip是一种无处不在的压缩方案：位进入，信息被重新安排和压缩，但是在您解压缩.zip之后出现相同的位。 (您不希望将压缩的Microsoft Word文档中的“ Z”更改为“ k”，只是因为它会使文件变小。)
There are many lossless image compression formats: TIF, TGA, BMP, RAW, PNG, SVG and PSD among them. Arguably, even GIF is a lossless format. Assuming that you are feeding them the best information possible, all of those formats will preserve data completely, without loss or change. The easiest compression scheme is run-length encoding: if there are several pixels of the exact same color one after the other in a horizontal line, rather than counting them separately, GIF makes a shortcut code for them (say “five red pixels”, rather than counting “one red pixel, another red pixel…” and so on). 无损图像压缩格式很多，其中包括TIF ， TGA ， BMP ， RAW ， PNG ， SVG和PSD 。 可以说，甚至GIF都是无损格式。 假设您正在向他们提供最佳信息，那么所有这些格式将完全保留数据，而不会丢失或更改。 最简单的压缩方案是游程编码：如果在水平线上有多个颜色完全相同的像素，而不是分别计数，则GIF会为它们创建快捷方式代码(例如“五个红色像素”，而不是计算“一个红色像素，另一个红色像素……”，依此类推)。
The major drawback to a lossless compression scheme (with the exception of SVG, which is predominantly a vector format) is file size. No matter how clever the algorithm, the data must be completely preserved. But what if we could change some of that data - squish it, alter it, or even throw it out - in such a way that the end user is unlikely to spot any changes? 无损压缩方案(主要是矢量格式的SVG除外)的主要缺点是文件大小。 无论算法多么聪明，都必须完全保留数据。 但是，如果我们可以更改某些数据(压缩，更改甚至丢弃)，以致最终用户不太可能发现任何更改，该怎么办？
This can’t be done with Word documents… but pixels are very small. If we can change some of them to be more like their neighboring pixels, we would increase the number of shortcuts we could take in describing the image, which in turn would reduce its file size. And that’s exactly what lossy compression does. There are a few lossy compression schemes for images; JPEG is the most well-known.
Word文档无法做到这一点……但是像素非常小。 如果我们可以将其中一些更改为更接近其相邻像素，则将增加描述图像时可以使用的快捷方式的数量，从而减少其文件大小。 这正是有损压缩的作用。 有一些针对图像的有损压缩方案。 JPEG是最著名的。
Lossy compression gives significant advantages in terms of file size. However, it comes with one major caveat: the changes made to the image to achieve this compression can't be undone. That is, the original information is lost, and can't be retrieved. (And no amount of digital wizardry can recover it - despite what the movies and television tell you). 有损压缩在文件大小方面具有明显优势。 但是，它带有一个主要警告：对图像进行的更改以实现这种压缩是无法撤消的。 也就是说，原始信息将丢失，并且无法检索。 ( 尽管电影和电视告诉您，但没有任何数字巫术可以恢复它)。
翻译自: https://thenewcode.com/62/Images-Lossy-vs-Lossless-Compression图像有损压缩与无损压缩
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• 无损压缩 Run-Length Lempel-Ziv Huffman 其他无损压缩算法都是由以上三类衍生出来 有损压缩 对于多媒体文件可以采用有损压缩, 比如jpg, mp3, mp4格式, 删除超越人类分辨力极限的信息, 不会影响实际的感官. 比如...
数据压缩
常用到的压缩方式分为无损和无损两类
无损压缩

Run-Length
Lempel-Ziv
Huffman

其他无损压缩算法都是由以上三类衍生出来
有损压缩
对于多媒体文件可以采用有损压缩, 比如jpg, mp3, mp4格式, 删除超越人类分辨力极限的信息, 不会影响实际的感官. 比如mp3删除20~20000HZ的波长区段信息可以缩减数据大小.


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• 一、数据无损压缩的理论——信息论 数据压缩的起源是基于信息论的。信息论之父香农第一次用数学语言阐明了概率与信息冗余度的关系。在1948年发表的论文“通信的数学理论”中，香农指出，任何信息都存在冗余，冗余...
• png无损压缩，可以轻松的压缩png文件，非常好用。
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• LZO是一个开源的无损压缩C语言库，其优点是压缩和解压缩比较迅速占用内存小等特点（网络传输希望的是压缩和解压缩速度比较快，压缩率不用很高），其还有许多其他的优点详细参考其网
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