JPEG image data is essential for web production. On the other hand, in order to build a website that is highly evaluated by
search engines
and is stress-free for users, it is necessary to reduce the amount of image data as much as possible and increase display speed.
In this article, we will explain how to compress and convert JPEG, as well as some useful free tools. We will also explain the differences between JPEG, JPG, PNG, etc. that you should know.
What is JPEG?
JPEG is an abbreviation for “Joint Photographic Experts Group” and is a data compression format for image files. To put it simply, it reduces the image quality of a still image such as a photograph or painting to such an extent that you can’t tell the difference at first glance, resulting in a “reduced file size.” This is a compression format used to save images with gradations or a large number of colors, and the extension
*
is “.jpeg” or “.jpg.”
By converting and saving images to JPEG format, you can reduce the file size while still expressing the full 16.77 million colors.
*An extension is a string of characters used to identify the type of file. It appears after a period at the end of the file name, with “.doc” for Word files and “.txt” for Notepad text files.
Characteristics of JPEG format
The compression rate of JPEG can be changed depending on the purpose, but since it is an image format that uses “irreversible compression”, you need to be careful when saving it. Once you save an image in low quality, you cannot restore it to the original quality or make it any higher quality.
If you do not want to reduce the image quality with JPEG, it is best to save the image when editing is complete, or save it as a separate file without overwriting it and keep the original image.
Since JPEG data is thinned out and degraded each time it is saved, there is a significant difference when comparing an image that has been saved once and one that has been saved several times. Please understand that if you perform editing such as repeated compression, uneven colors, fading, and blurring may appear.
History of JPEG
JPEG is a format standardized by the Joint Photographic Experts Group, a joint group of the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Union (ITU). BMP and GIF had already been standardized before JPEG, but each had their shortcomings, so JPEG was standardized to compensate for them.
Although it was a standard from an era when communication speeds were still slow, JPEG came to be used by many people because of its versatility in terms of compression and transfer.
Background of the birth of JPEG
In 1995, when the Internet began to spread in Japan, the so-called “first year of the Internet,” JPEG was developed with the aim of reducing the size of large-capacity, high-quality image data such as photographs. Ta.
At that time, BMP and GIF were the main image data formats until JPEG was developed. However, there were problems such as “BMP has good image quality, but the capacity is too large,” and “GIF has a small capacity and is lightweight, but the number of colors is too small.”
Around 1995, Internet connections were mainly based on dial-up connections and pay-as-you-go rates, so there were technical limits to communication speed. Due to this background, it was difficult to send and receive large files such as BMP files online. Therefore, JPEG was developed, which can be expected to significantly reduce data by performing lossy compression and omitting some data.
With dial-up connections at the time, GIF still had an advantage in terms of transfer volume and speed for CG illustrations, but due to a patent issue with GIF by Unisys in the US, the GIF format could no longer be used freely. Ta. For this reason, JPEG has become widely used as an alternative to GIF.
Standards submitted in 1994
As explained in the “History of JPEG” section above, the JPEG image format was developed by the joint efforts of three organizations: the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Union (ITU). It was standardized by the group “Joint Photographic Experts Group (JPEG)”.
The standard was submitted to the Japanese Industrial Standards (JIS) in 1994, and the following year, in 1995, it was standardized in Japan as “Standard Number: JIS X 4301.”
reference
- Digital compression and encoding of continuous tone still images – Part 1 Requirements and guidelines
- Japan Document and Information Management Association, Public Interest Incorporated Association, Image Compression Guidelines for Digitized Documents
Main uses of JPEG
The main uses of JPEG include:
View photos
JPEG can handle an extremely large number of colors, 16.77 million colors (24-bit full color), and can express color transitions such as gradations beautifully. Although it can handle a large number of colors, it uses very little data, making it suitable for publishing photos online.
For example, when taking photos, you can shoot in RAW format, which is uncompressed and holds a large amount of data, and when posting photos online, you can compress them into JPEG before publishing them.
Web publishing
JPEG has high image quality but uses very little data, so it can reduce the loading speed of web pages. It is suitable when you want users to download image content, as it allows users to access content without stress and does not take up too much
cloud
storage space.
Differences between JPEG and other file formats
Below, we will explain the differences between JPEG and other file formats.
Difference between JPEG and JPG
Regarding JPEG and JPG, the only difference is the extension when saving, such as “.jpeg” and “.jpg”, but the basic functions remain the same. The reason why there is a difference between “.jpeg” and “.jpg” in the JPEG extension is due to the “OS (Operating System)” created by Microsoft.
The OS called MS-DOS, which was originally mainstreamed by Microsoft, was used as the basic software for general PCs until the rise of Windows. In the MS-DOS era, extensions were limited to three characters or less, so JPEG was “.jpg”. Later, when Windows became the norm, there was no longer a limit on the number of characters, and “.jpeg” began to be used.
Currently, the notations “.jpeg” and “.jpg” are mixed, but it can be said that “.jpg” is the more commonly used notation. However, keep in mind that there is no technical difference between “.jpeg” and “.jpg”, so it doesn’t matter which one you use.
Difference between JPEG and PNG
PNG (Ping/Ping) is an abbreviation for “Portable Network Graphics” and is a data compression format similar to JPEG. The extension is “.png” and is often used to save simple images such as illustrations, graphs, logos, etc.
PNG is a relatively new file format that was originally developed as an alternative to the GIF data format due to patent issues. GIF is characterized by its small file size and light weight, but it can handle only 256 colors, making it difficult to express colors delicately.
In contrast, the newly developed PNG supports two formats: a 256-color format like GIF, and a larger format that can express 16.77 million colors, allowing for clear line drawings and graphics. It can also be displayed beautifully.
It also supports “transparency,” a feature that JPEG does not have, so the point is that you can freely set the transparency from semi-transparent to completely transparent. Furthermore, because it is a “reversible compression”, there is no deterioration even if the data is compressed, and the image can be restored to its original state even after compression. In other words, no matter how many times you save the image, the image quality will not deteriorate.
For example, Windows screenshots are automatically saved in PNG format. This is because PNG can preserve lines such as text and color boundaries more clearly than JPEG.
However, the file size of PNG may be larger than that of JPEG compression format. When using on a website, be aware that heavy image files will place a heavy burden on the server and affect the display speed of the web page.
It is important to understand the difference between JPEG and PNG and change the compression format depending on the purpose, such as PNG for images that require transparency, line drawings, logos, illustrations, etc., and JPEG for images posted on websites. .
Difference between JPEG and PDF
As mentioned above, JPEG is mainly suitable for storing images such as photos. Image data that would normally be stored in a large capacity can be compressed and saved in a small capacity.
On the other hand, PDF is suitable for storing text data. Although the data compression size can be changed, the capacity will not be significantly smaller than JPEG.
When text data is saved as PDF, the text appears more clearly when printed than when saved as JPEG. Due to these characteristics, PDF is used to save all kinds of text data such as invoices, receipts, and business documents.
Also, since JPEG is irreversibly compressed, the image quality deteriorates each time it is saved, but the image quality of PDF does not deteriorate even if it is saved repeatedly. If you use JPEG, the text may become unreadable after saving it several times, so to avoid such situations, PDF is recommended for text data.
Difference between JPEG and TIFF
Both JPEG and TIFF are suitable for storing image data, but TIFF has a very large file size. Since TIFF is a reversible compression, the image data is not lost even when saved, and all data contained in the image is saved as is.
Even if the storage capacity is a few megabytes when saved as a JPEG, the storage capacity can reach hundreds of megabytes, or even gigabytes, when saved as a TIFF. Therefore, it is not suitable for use on the web, and is often used by photographers to preserve images in a clean state.
Difference between JPEG and BMP
BMP is the oldest image format, developed by Microsoft and Aldus in 1986. Aldus later merged to become Adobe.
BMP is not compressed when saved, and the data that can be saved is kept as much as possible. Therefore, the image data tends to be larger than JPEG.
BMP is a format designed to retain as much information as possible. Therefore, if you want to compress the BMP data size, you need to do it manually. If you want to restore a compressed image to its original state, you can uncompress it, but the process takes a very long time.
Advantages and disadvantages of JPEG
Although JPEG has established itself as a standard image compression format, it has both advantages and disadvantages. From here, I will explain the advantages and disadvantages of JPEG.
Advantages of JPEG
The advantages of JPEG include the following.
High quality
JPEG supports 16.77 million colors (24-bit full color), so it has extremely high image quality. Landscape photos can be reproduced while preserving natural gradations and colors. In addition, since the white balance and saturation are set at the time of shooting, it is convenient to import the image into image editing software and process it after shooting.
High compression ratio
Although JPEG has the inconvenience of being irreversibly compressed, it can be compressed at a very high compression rate while preserving image quality. Its compression rate is an order of magnitude higher than lossless compression such as GIF.
You can also specify the compression rate for JPEG. The higher the compression rate, the smaller the data capacity, but the rougher the image will be. If you want to reduce the size while maintaining a certain level of image quality, you need to set the compression rate appropriately.
Supports progressive formats
JPEG supports an extended specification called progressive. It is also called “progressive JPEG”.
When displaying a JPEG image online, it is usually displayed using a display method called baseline, in which the image is read and drawn in order from the top of the image. However, with this display method, if the image is heavy, it will take time to display the entire image.
On the other hand, with images saved in progressive JPEG format, the entire image appears rough when loading begins, and gradually becomes clearer as loading progresses. By transmitting data in pieces using a mechanism similar to interlacing in GIF, it is possible to quickly display the entire image of a heavy image even over a slow connection.
Highly versatile
Images in JPEG format are highly versatile and can be used in most browsers. Also, if you want to import it into a software or application and edit it, it will work fine in most cases. One of the major benefits is that it can be used without having to choose hardware such as smartphones, digital cameras, and scanners.
Disadvantages of JPEG
The disadvantages of JPEG include the following.
Image quality deteriorates with each compression
With JPEG, the image quality deteriorates each time the image is compressed. Although there may be no visible changes after several compressions, advanced technology removes colors that cannot be seen with the naked eye.
Additionally, if compression is repeated, phenomena such as the white balance adjustment range becoming narrower will occur, and blown out highlights and crushed shadows will become noticeable.
Degraded image quality cannot be restored
JPEG images that have been repeatedly compressed and degraded cannot be restored to their original image quality. This is called irreversible compression. Data that is difficult to see with the naked eye is deleted and saved, making it impossible to restore it. On the other hand, lossless compression reduces the file size by calculating the data, so it can be restored even after compression.
Does not support background transparency
Unlike PNG, JPEG cannot have a transparent background. Therefore, if you convert a PNG format image with a transparent background color to a JPEG format image, the background color will be painted white.
Because of these characteristics, JPEG is not suitable for tasks that involve overlapping or compositing multiple images to create a single image. When performing such work, it is necessary to prepare the data in PNG or other format.
JPEG compression method
Uncompressed image files called “BMP (bitmap)” have good image quality, but are quite large in size.
When using heavy images on websites or attaching them to emails, it is important to compress them in JPEG format to reduce the file size. Now let’s take a look at how compression works.
How JPEG compression works
JPEG compression uses a method called “discrete cosine transform (DCT),” which divides an image into components (patterns) and assigns numerical values to each component.
Specifically, the original image is divided into 8 x 8 blocks, the data is quantized (transformed) using DCT operations, and it is decomposed into high-frequency components and low-frequency components. Then, the necessary information on the low frequency components is thinned out for each blog, without taking in the information on the high frequency components. However, since the difference is almost invisible to the human eye, it is possible to reduce the amount of data while maintaining image quality.
If you want to compress a JPEG, open the file in “Paint” on Windows, “Resize” it, and then click “Save As” to complete the compression. It is best to save the file type as JPEG (“.jpeg” or “.jpg”). You can check the size and size by right-clicking on the image and selecting “Properties”.
When you want to compress a large number of images at once, it is convenient to use external tools such as “TinyPNG”, “Compress JPEG”, and Google’s “Squoosh”, which can compress JPEG or PNG files by simply dragging and dropping them. .
How to compress JPEG with free tools
From here, we will introduce the free tools mentioned in the previous section.
TinyPNG
TinyPNG
is a free image compression tool. In addition to JPEG, “PNG” and “WebP” are also supported.
There is also a WordPress plugin that automatically compresses all images when used in WordPress. Intelligent compression was added in 2014, allowing you to compress images while maintaining crisp image quality.
How to use (JPEG compression method)
Compressing JPEG is very easy, just drag and drop the file you want to compress to the specified location on the site.
After that, two buttons will be displayed: “Save to Dropbox” and “Download All”, so select either one to download.
Compress JPEG
Compress JPEG
is a free tool that can compress up to 20 files at the same time. In addition to JPEG, it also supports “PNG”, “GIF”, “PDF”, etc.
A distinctive feature is that you can adjust the quality of JPEG compression yourself. If you switch to manual mode, you can adjust the image quality from 1 to 100. Additionally, all uploaded data is automatically deleted after one hour, so you can rest assured about your privacy.
How to use (JPEG compression method)
1. Check the extension of the file you want to compress and select from “JPEG”, “PNG”, “GIF”, and “PDF”
2. Drag and drop it to the specified location and it will be automatically uploaded and a thumbnail will be displayed.
3. If you want to download the compressed data as is, click “Download All”
4. If you want to adjust the image quality, double-click the displayed thumbnail
5. The image quality adjustment screen will be displayed immediately below, so click “Download All” after making adjustments.
Squoosh
Squoosh
is a free yet highly functional compression tool. It also has functions such as resizing uploaded images, adjusting the number of colors, and dithering to reduce image quality degradation.
Also, if you want to adjust the image quality, you can change it. It also has functions such as image quality rotation and smoothing.
How to use (JPEG compression method)
It is very easy to use, just drag and drop the file to the specified location and the screen will switch to the editing screen. On the editing screen, you can adjust the “resize”, “color number adjustment”, “dithering”, “image quality”, etc., so adjust them and then click the download button.
How to convert JPEG or PNG
Image extensions can be easily converted using Windows default functionality or external tools. Check out how to convert JPEG to PDF or convert PDF to JPEG below.
Convert JPEG or PNG to PDF
To convert JPEG or PNG to PDF on Windows, “right-click” on the JPEG or PNG file and select “Print” to display the screen for printing the image.
Select “Microsoft Print to PDF” from “Printer” displayed at the top left, and click “Options” at the bottom right of the screen to display the “Print Settings” screen. After determining the “Print Orientation” in “Printer Properties”, click “Print”.
This will take you to the save screen, so make sure the “Save as type” is set to “PDF document” and click “Save”.
“LightPDF” and “Soda PDF” are famous external tools for converting JPEG to PDF.
How to convert JPEG or PNG to PDF with free tools
From here, we will introduce the features and usage of the free tools mentioned in the previous section.
LightPDF
LightPDF
is a free conversion tool with a huge number of features. You can convert JPEG and PNG to PDF, and vice versa.
You can also perform a wide range of conversion tasks such as “Excel/Word to PDF” and “PPT to PDF.” Additionally, you can edit the PDF itself, split, combine, and compress it.
How to use (how to convert JPEG or PNG to PDF)
1. Click on the item you want to work on from the home screen
2. On the screen that appears, drag and drop the file you want to convert to the specified location, or click “Select File” to upload it.
3. Set “page orientation”, “page size”, “margins”, etc. from the conversion settings
4. Click the “Convert” button to convert
Soda PDF
Soda PDF
is a free tool that can not only convert JPEG and PNG to PDF, but also convert PDF to files with other extensions.
One of its most distinctive features is the ability to convert HTML to PDF and vice versa. Using this feature, you can save images such as website captures as PDF data. You can also convert files with various extensions to PDF.
How to use (how to convert JPEG or PNG to PDF)
1. Drag and drop the file you want to convert to the specified location on the web page
2. The file will be converted automatically, so click “Download file” on the screen that appears.
Convert PDF to JPEG or PNG
Contrary to converting JPEG to PDF, you can also easily convert PDF to JPEG. Conversion software such as “iLovePDF” and “Smallpdf,” which can be converted on a website and does not require installation, and “Adobe Acrobat,” are also useful tools.
How to convert PDF to JPEG or PNG with free tools
We will introduce the features and usage of the tools listed in the previous section.
iLovePDF
iLovePDF
can convert PDFs to JPEG and PNG, as well as combine, split, and compress PDFs. You can also convert PDF to Word, Excel, PowerPoint to PDF, and many other extensions.
How to use (how to convert PDF to JPEG or PNG)
1. Select the desired work item from the home screen
2. Drag and drop the file you want to convert from the displayed screen to the specified location, or click “Select PDF file” to upload the file.
3. Select the image quality and then click the “Convert” button
Smallpdf
Smallpdf
not only allows you to convert PDF to various extensions such as Word, Excel, and PowerPoint, but also has functions that allow you to add page numbers to PDF, protect and lock PDF, etc. It also has a PDF scanner function, which allows you to create a PDF from an image scanned with a smartphone.
How to use (how to convert PDF to JPEG or PNG)
1. Select the desired work item from the home screen
2. Drag and drop the file you want to convert from the displayed screen to the specified location, or click “Select File” to upload the file.
3. It will be converted automatically, so click the “Download” button after the conversion is complete to download it.
Adobe Acrobat (paid)
Adobe Acrobat
is a PDF conversion tool that is available for a fee (some are available for free). There are only tools provided by major companies, and they are compatible with almost all extensions.
In addition to functions such as merging, splitting, and compressing PDFs, it also has almost all the functions necessary for editing work such as deleting, rearranging, and trimming pages.
How to use (how to convert PDF to JPEG or PNG)
1. Select the desired work item from the function introduction page
2. Drag and drop the file you want to convert from the displayed screen to the specified location, or click “Select File” to upload the file.
3. Click the “Convert” button to convert
4. Once the conversion is complete, a “Download” button will appear, so download it.
summary
JPEG is an image file compression format that is suitable for saving photos with a large number of colors or gradation images taken with a digital camera. There are two extensions: “.jpeg” and “.jpg”, but there is no difference between them.
It is characterized by its ability to reduce image size, and by converting images posted on websites to JPEG format, the display speed can be increased. However, it is important to understand that the image quality will deteriorate each time it is saved due to lossy compression.
On the other hand, PNG is reversibly compressed, so it does not deteriorate even when compressed. PNG is suitable for images with few gradations, clear outlines and borders, or images that require transparent colors.
There are many different image storage formats, so it’s important to understand their differences and characteristics so you can handle images appropriately.