The JPEG file extension is usually associated with image files and is one of the most popular image formats currently in use. It uses a lossy compression algorithm developed by the Joint Photographic Experts Group. JPEG files are commonly used for storage digital image data and computer graphics. A JPEG file contains metadata with additional information such as color space, color profile, and image size.
JPEG and JPG
An extension, a format that is interchangeable with JPEG, is the most popular of the two.
JPEG compression method
JPEG uses a lossy compression algorithm, that is, some image information is lost and cannot be recovered. Although this compression method significantly reduces the size of the image, it is achieved due to lower image quality. However, JPEG offers acceptable image quality despite a sharp reduction in file size. In addition, the user can select the compression level when converting the image to JPEG to achieve the desired quality.
JPEG format specification
A JPEG file stores up to 24 bits of data per pixel, which means that it supports a full color palette. The JPEG format is further subdivided into 2 sub-formats - JPEG / Exif and JPEG / JFIF . The first is used in photography, and the second is the Internet standard. Exif and JFIF standards define the popular JPEG-compressed image format.
JPEG Digital Photo Format This is one of the most popular photo storage algorithms. It was developed in 1987 by a group of joint photography experts. In English, this is written as the Joint Photographic Expert Group. According to the first letters of these words, the format was named, which is pronounced as "jaipeg".
The JPEG file format was originally created for the transmission of digital images, including photographs and texts, through digital and fax communication channels. For this, a standard for compressing graphic information data was developed, the files of which can have the extensions jpg, jpe, jpeg or jfif.
The algorithm for storing graphic information embedded in the JPEG file format is a lossy compression method that allows you to compress data at a fairly high speed and efficiency. In JPEG format, photographs can be saved with a color depth of up to 24 bits / pixel and a side size of not more than 65535 pixels (2311.93 cm).
JPEG photo file compression
The process of compressing a digital photograph in JPEG format is not carried out immediately, but in stages. The first step is to convert the digital image from the RGB color space to YCbCr. In it, the Y component is responsible for the brightness of the image and is fully encoded. The Cb and Cr components are color difference channels. They reduce color information (Fig. 1).
Fig. 1 Color correlation in JPEG format for converting photos from RGB color space to YCbCr.
Then the whole photo is divided into individual 8x8-pixel squares, and conversion is performed on each of them. At the same time, each square in JPEG format is decomposed into composite colors to calculate the frequency of their appearance throughout the photo field.
This analysis allows you to select the necessary information about the upper range of the color spectrum of the image and partially get rid of it. In this case, the part of the brightness information of channel Y associated with the channels Cb and Cr is also discarded. This is almost not noticeable in photos, but it allows you to reduce the size of JPEG files.
The amount of information removed from the JPEG file during such processing depends heavily on the specified compression level, and the larger it is, the worse the quality of the photo. The image obtained in this way can never be returned to its original form. It is for this reason that JPEG is called lossy compression format (fig. 2).
Fig. 2 Example of an enlarged fragment of a JPEG photo with a different compression level.
At the final stage of JPEG compression, the colors and brightness of the image are encoded. In this case, only differences of 64 pixel squares are saved, and all the same information is deleted. Then the results of such coding are represented by numbers, which are also compressed by a special algorithm.
The file size after compressing a photograph in JPEG format compared to the original file depends on the detail of the image and the more small details, the larger the file size. Those photos are better compressed where there is less noise and more smooth color and brightness transitions. The higher the contrast, the worse the photo is compressed (Fig. 3).
Fig.3 Files of these images in TIFF format are 168 Kb in size. In JPEG format, the left photo is 12 KB, and the right is 29 KB. The difference between the images is only in color noise.
To view photos encoded in JPEG format, you must first decode them. This process is also performed by a special program in stages, but in reverse coding order. In this case, the transition from the YCbCr space back to RGB proceeds according to other predefined relationships (Fig. 4).
Fig. 4 Ratios of YCbCr components in JPEG format for transferring photos back to RGB space.
Benefits of JPEG Photos
The JPEG format has gained popularity in digital photography due to the fact that its compression algorithm allows you to greatly compress the information and at the same time maintain smooth transitions of brightness and color. JPEG files may be small in size and still maintain acceptable image quality.
This format is used in all digital cameras for storing received photo frames. All photos saved in JPEG format can be used immediately for their intended purpose. They optimally selected brightness, contrast and saturation. For their completion does not require any special program. Everything is done in the camera (Fig. 5).
Fig. 5 Examples of the stylistic settings of the camera for JPEG photos.
In addition, when taking photos in JPEG format, the image processing and encoding process takes much less time than, for example, in the format. This allows you to increase the speed of serial photography and the number of frames shot, which is very important for such genres of photography as “Sport” or “Reporting”.
JPEG photos can be viewed without any problems on any electronic device that has such a function: TV, computer, tablet, cell phone, game devices and others. This image encoding standard is universal. It is supported on all major platforms - Windows, Mac OS, Linux, Android, iOS.
The size of JPEG files allows you to quickly send photos via communication channels, which makes it indispensable for the Internet. This format is the main for posting photos on photo sites, forums and social networks.
JPEG flaws for photos
The main disadvantage of JPEG photos is that they cannot be saved again. After each saving of such files, they lose image quality and the higher the level of compression, the worse their quality. For this reason, it is not necessary to save the results of intermediate processing of photos in JPEG format (Fig. 6).
Fig. 6 An example of a fragment of one photograph before and after three times saving in JPEG format with medium quality.
Another disadvantage of the JPEG format when editing photos is that it does not save layers and alpha channels. For example, you cannot postpone the processing of photographs using masks or adjustment layers and return to this work later (Fig. 7).
Fig. 7 An example of complex photo processing in Photoshop, the results of which cannot be saved in JPEG format.
In addition, when editing digital photographs often require a large color depth, and in JPEG format it is limited to 256 values \u200b\u200bper channel. This is not enough for high-quality color reproduction and is also a disadvantage of JPEG photos.
The above disadvantages of the JPEG format create limitations in the photographer’s work to improve photos after taking photographs, but there are still others. They degrade the image quality of a photograph immediately when it is saved to the camera or when scanning film. These disadvantages include the following seven.
1.Distortion of color.
2. Loss of detail.
3. Deterioration of sharpness.
4. Ghosting around the contours.
5. Stepping lines.
6. The appearance of noise.
7. Mosaic.
These disadvantages of JPEG photos directly depend on the level of information compression. In order to minimize losses, you should always keep the source of digital photos with the lowest possible compression, or in another way with maximum quality. At the same time, there are different scales for choosing the quality of photos.
JPEG photo quality scale
When saving digital photos in JPEG format, the degree of compression of information in relative units is always set. Most often, a scale from 1 to 10 or up to 12 is used for this (Fig. 8).
Fig. 8 Photoshop program window for saving photos in JPEG format on a quality scale 1 - 12.
For a more accurate setting of the compression level, smaller scales are also found, for example, from 1 to 100. This scale is used to save photos in JPEG format during scanning (Fig. 9).
Fig. 9 TWAIN driver window for saving photos in JPEG format when scanning on an Epson scanner.
Sometimes, to save photos in JPEG format, more compact scales are used, consisting of only five or three positions. In such scales, it is not compression of the photo that is selected, but the quality of its image, not in numbers, but in Russian or English words (Fig. 10).
Fig. 10 One of the windows of Photoshop for saving photos in JPEG format on a simplified scale.
The simplest scale for selecting the quality level for JPEG photographs is used in digital cameras. It consists of only three positions that determine the conditional size of the photo file. They are indicated by the letters of the English language “L”, “M”, “S” from the words Large - large, Medium - medium, Small - small (Fig. 11).
Fig. 11 Two quality scales of JPEG format for saving photos in a digital camera.
When saving digital photos in JPEG format, it is important to remember that on different scales a large number can correspond to the image quality () and its compression ratio (). At their core, they are the exact opposite.
In the first case, a larger number corresponds to the maximum image quality, and in the second case, the minimum. When saving a JPEG file, it is easy to make a mistake and degrade the quality of the photo, which then cannot be restored. And besides this, the JPEG format has other features of saving photos that you must know.
How to save photos in JPEG format
Given all the advantages and disadvantages of the JPEG file format, you must be able to correctly use it for photographs for various purposes. This helps to save disk space for their storage and at the same time maintain high quality image quality.
The main mistake of many photographers is a misunderstanding of the very principle of compressing information in the JPEG file format. This leads to the fact that photographs of other more “heavy” graphic formats are converted to JPEG format to save space, processed several times and at the same time they are compressed very much.
All this can only be done with copies of photographs intended for specific purposes. It is always important to remember that the JPEG format is primarily intended for efficiently viewing photos or for printing them. But this is only in those cases when the photos do not need to be modified after taking photos or after scanning.
To improve the quality of JPEG photos, you must first convert them to TIFF or PSD. Copies of files of these formats are large, but they do not have the disadvantages inherent in JPEG files. Once again, photographs can be returned to JPEG format only after their final processing (Fig. 12).
Fig. 12 Improving the quality of JPEG photos.
For all options for saving digital JPEG photos, you must always set the sRGB color profile. It is supported by all graphics programs, all technical devices, and on all platforms. This allows you to see photos everywhere the same.
Although JPEG also supports other color spaces, because of their large color gamut, some colors will be cropped, and such photos will look different everywhere. To save other color profiles with a large number of colors, you need to use other file formats. Read about them in the following articles.
Published in the collection of programs: November 19, 2010
Operating system: Windows
The size of the program (distribution): 1571 Kb
Type of license: Freeware
JPG / JPEG photo converter, many photo formats such as BMP, GIF, PNG, TIF, ICO, EXIF, WMF, EMF, JPG / JPEG file with some useful options have changed.
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Adobe Photoshop CS6 for Microsoft Windows
Adobe Photoshop CS6 for Microsoft Windows is an image editing and managing software downloadable on Windows computers, namely Windows 7 (without SP and with SP1) and Windows XP with SP3. This software comes with new features and tools for easy, quick, fun and advanced editing of digital images. One feature that makes this program reliable for image editing is the Adobe Mercury Graphics Engine, which is an engine technology that provides faster and high quality performance. Content-Aware tools are new features designed for retouching images with ease as you can crop images without any effect, auto-correct blurriness or wide-angle lens curvatures, remove red eye, and adjust color balance like brightness and contrast. This image editor is also bundled with auto-recovery feature that can backup any unsaved images, Background Save option, Blur Gallery, Crop tool, video creation, and a whole lot more. With all these new improved features and a modern friendly-user interface, editing digital photos can never be so fun and easy without Photoshop CS6. 
Adobe Photoshop CS6 for Mac
Adobe Photoshop CS6 for Mac
Adobe Photoshop CS6 for Mac is the version of à ¢ €Š“Creative Suiteà ¢ € image managing software designed exclusively for Mac computers, particularly Mac OS X v10.6 to 10.7 in 64-bit. This image editing program is bundled with a new set of features and tools, such as the Mercury Graphics Engine developed by the same company for fast and high quality image enhancing performance, Content-Aware features, intuitive re-imagined tools for movie designing, workflows , Blur Gallery, Crop tool and a whole lot more. The Adobe Mercury Graphics Engine functions in a way that it makes editing task easy and fast to complete. This also allows the sharing and migration of images with auto-recovery and Background Save options. The new Content-Aware tools are made for easy and controllable way of retouching or enhancing images that result in a more satisfied output. It basically lets any user to auto-correct images, crop them and correct wide angle lens curvatures. 
ACD Systems Canvas 14
ACD Systems Canvas 14
ACD Systems International Inc. is the developer of ACD Systems Canvas 14, which is a technical graphics solution software, that enables users to analyze data, enhance graphics and share all information with ease and rapidness. This program is designed with full-featured tools that assist users in making technical graphics and illustrations with accuracy. It consists of editing tools that vary from image editing to object illustration tools. Any results created by this program make good presentations for projects, proposals and other purposes for any line of business related to graphics and engineering. More on the features, users can work with raster images and vector graphics using the same file with the option edit by resizing and scaling objects, drawing shapes, as well as inserting stroke and fill inks or widths. There is also a tool for adding texts or labels and format dimensions, plus creating charts. With this program, users can share finished projects through presentations or publications.ACD Systems ACDSee 15
ACD Systems ACDSee 15
ACD Systems ACDSee 15 is a photography software that features an image organizer, viewer, and RAW / image editor program for Microsoft Windows and Mac OS X 10.6 (Windows XP with Service Pack 2, Vista, 7 & 8; Mac OS X 10.5, 10.6 , 10.7 and Mountain Lion). It was developed by ACD Systems International, Inc. and originally distributed as a 16-bit application that was later upgraded with a 32-bit version. This minimum hardware requirement for this application is an Intel Pentium III / AMD Athlon processor or equivalent with 512 MB RAM (with 310 MB free hard drive space), a high color display adapter at 1024 x 768 resolution, and a CD / DVD burner. ACDSee manages and supports video and audio files in formats that include GIF, BMP, JPG, PNG, MP3, PSD, WAV, MPEG, and TIFF. Users can view, edit, add effects, and organize photo and video collections that can be shared online. Photos can be organized as these are imported from the camera or other storage device. It also features Map view and geo-tagging support that enable users to view the location of images from GPS-enabled cameras. Features like fast browsing, scanning, editing, and backup options facilitate sorting of photos by date and event, and storage of backup copies to CD, DVD, and Blu-Ray.It is pronounced as a “jeep” and encompasses the abbreviated name of the organization - the developer of this format, the Joint Photographic Experts Group.
How to determine the image format
Extensions help determine image format. Popular extensions for jpeg format files: .jpg, .jpeg
Go to the folder with the desired image, find it in the list and move the cursor over the image (with the mouse arrow). Usually, information about the type of drawing and size immediately pops up.
If this does not happen, click on the image of the right mouse button and go to the properties. It will indicate the type of file, its size, location on the computer, the amount of space that it occupies on the disk and the date it was created.
Convert image to jpeg format
Any program for editing pictures and photos can convert an image to jpeg format.
The simplest such program is the Paint program. Along with notepad and calculator, it is in almost any operating system.
Right-click on the desired image. In the window that appears, select the function: "Open with ...". Another window pops up with a list of programs available on your computer that are suitable for editing images. Feel free to choose Paint (an icon with a palette and a brush).
In the Paint program, you can independently resize the image by selecting the "Resize" function. You can change the size both in pixels and in percentage. Mark the desired action with a dot (pixels or percentages) and set the horizontal and vertical sizes. In order for the picture to retain its appearance, do not remove the checkmark from the "Save aspect ratio" function.
You can also slightly adjust the picture using the appropriate tools of the program. By pressing the “F1” key, you can call up a window with help information about the program and the possibilities of working with it. It is not recommended to adjust photographs in this program, since subsequently they can have the effect of a picture.
Do not be afraid to accidentally click somewhere and ruin the image! You can always press the ctrl + z keys at the same time and undo the last action. In the Paint program, you can undo the last three actions in a row.
If everything suits you in the image and you just want to change the format, press the F12 key. In the window that appears below, enter the file name and select the jpeg format from the list of formats. Check the save path in the line under the words “Save As” and click the “Save” button. Your image will automatically be assigned the extension .jpeg.
In addition to Paint, you can use a photo converter to convert the image to jpeg format. You can read that, as well as download the free demo version for 15 days at http://www.photoconverter.ru/help/tutorials/convert_to_jpg.html
Change images to your liking!
