Friday, July 7, 2017

What are the most popular image formats? Which is better in each case?

Today we bring you a slightly different article. Today we are going to teach you which are the most popular image formats , and which is better in each case to save your images.

Formats for storing images

A few weeks ago we brought you the news that the patent on the MP3 format had finished , but we also took the opportunity to tell you a little about the audio formats.
For today we will discuss a similar topic. Let's explain which formats to save images are the most popular, and we will explain which are the best in each case.
There are multitude of image formats, and each one has its goodness and flaws.
There are multitude of image formats, and each one has its goodness and flaws.

Lossless Formats

Let's start with lossless formats . This means that images are saved without losing quality . Therefore, they are the formats that occupy most on disk.


Undoubtedly, this is the best known lossless format. Its name comes from " Portable Network Graphic" , and saves the images without affecting its quality. In spite of this, it does compress the image, but in this case it is a lossless compression (because the quality is not reduced).
This format is widely used . For example, it is the one used by the iPhone to save the photos taken with the cameras, or for the screenshots. Also, Apple also uses it for Mac screenshots (by pressing Cmd + Shift + 3/4 ). Their use on the Internet is also quite widespread, although not as much as lossy formats, as their file size is high and using them on web pages would slow down the upload of them. For all this, this is my preferred format when I want to save images without loss of quality .
One of its main features is that it allows alpha layers  In this way, the images can have transparencies and shadows .
PNG, along with JPEG, two of the most popular image compression formats.
PNG, along with JPEG, two of the most popular image compression formats.


Well ... I think you do not need presentations ... Thanks to the Internet the GIF format became very popular. This is the format used to create the typical animations , which is why it became tremendously popular.
Actually, with GIF what is done is to save several images, which will be the ones that when passing quickly will create the animated image effect. In addition, it shares certain features with PNG. Just as PNG uses a lossless compression algorithm to reduce file size, specifically LZW. It also has an alpha layer  for transparencies, as does your brother ... static ...
A GIF can have a collection of images that when passing one after another remains the animation effect.
A GIF can have a collection of images that when passing one after another remains the animation effect.


Maybe if you are a user of macOS and iOS, which is most likely if you are viewing this web, do not sound this format. And it is that the BMP format , or  Windows Bitmap , is preferred of the Windows operating system Thus, it is for example the default format in Microsoft Paint .
While this format also performs some lossless compression, it is not as effective. In this case the compression simply uses the RLE algorithm, which we will mention in more than one occasion. Basically what this algorithm does is look for patterns . And although its operation is very simple to understand, I do not consider it opportune to explain it in this article, but if you want it, we can explain it in a future article.
Unlike PNG, this format is practically in its last . Out of Windows systems is hardly used, as it offers a very low compression ratio when compressing with RLE.
BMP is the default format in Microsoft Windows for lossless compression images.
BMP is the default format in Microsoft Windows for lossless compression images.


TIFF is a special format. In this case, it is the user who can choose what to do with the image. In this way, the person who saves the image can decide whether to save it without compressing or to compress it with LZW or Packbits.
In either case the compression is lossless, so the quality is not affected. Apple uses this format in the "Capture Image" application or when scanning a document, for example.


This format is used by digital cameras . All, or almost all, digital SLR cameras allow you to save your photos in this format. And it is the one that I use when I take pictures with my camera (later if I want and I will export them with the computer to JPG, for example).
Although there are many RAW formats, it depends on the manufacturer, they have characteristics in common. Images saved in RAW are a direct representation of what the sensor captures , as well as containing additional information about the camera and the parameters used. Therefore, this is the perfect option if you want to retouchsomething in the photographs you make. Therefore, whenever I can take the pictures in RAW, it is the one that will give me the best quality, although the counter will occupy more (approximately 1 MB per Megapixel).
And how can we identify this format? The extensions of the most used files are: * .nef , * .dng , * .orf and * .raw .
To get the best from your digital camera, take the photos in RAW.
To get the best from your digital camera, take the photos in RAW.

Lossy Formats

We changed category. Now we go to lossy formats. These formats will compress morethan the previous ones, but on the contrary will lose quality . And how much? That will depend on the format, plus the settings of each format.


Undoubtedly, this is the most popular format in this category. And maybe I'm launching, but I dare say it's the format most used currently.
Its acronym comes from Joint Photographic Experts Group " , the group that developed this technology. This is the format preferred by web pages , as they result in good quality images but with a low file size. In addition, the compression ratio is configurable , allowing compressing more or less, sacrificing more or less quality, according to our needs.
Selector of quality in JPEG.
Selector of quality in JPEG.
Obviously this would not be possible without a lossy compression algorithm. Therefore, it uses a technique that consists in realizing the discrete transform of the cosine (DCT) in order to be able to approximate the values ​​of the most important components. As you approach, the image will occupy less, but of course, the approach is not a reversible operation ... In addition to this, it also makes use of RLE to compress the resulting data. Obviously I am aware that this last paragraph has been understood by few people, but it is a very broad and complex subject. Still, if there is anyone interested we can do an article explaining more in detail how the image compression is done step by step (and maybe some code example drops).
Steps to compress in JPEG.
Steps to compress in JPEG.
Finally, mention that this format is becoming outdated . That's why more and more alternatives come up, like JPEG 2000 or JPEG XR. But none ends up curdling ... Still, this is the format that I use to compress my images and photographs.


This is an image compression format developed by Google . While this format allows both compressing images and not, it is mainly known for the former.
This compression format obtains better compression ratios . That is why Google is the format recommended for web pages (hence its name carries the word "web"). Even so, this format is not yet widely used.
WebP, the Google format.
WebP, the Google format.


As you can see, there are many image formats, with and without loss. Obviously I have not all commented here, that would be very difficult. Still, I wanted to make special mention of vector- based image formats In this article we focus on the formats that save the images as collections of pixels, but the truth is that there are formats, such as SVG (which uses XML), which actually save the vectors or lines of the image. This allows for infinite zooming, but its limitations are obvious. It is good for representing geometric figures or drawings, but they can not be used for complex pictures or images.
What do you think? What format do you use in each case? Would you like us to bring a similar article but with video formats? Would you like us to explain in detail how the JPG format works, for example?
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