JPG images: A complete guide for the JPG file format

The JPEG (Joint Photographic Experts Group) format, commonly known as JPG, has a fascinating history that dates back to the late 1980s. The group was established with the aim of creating a standard for image compression, enabling efficient storage and transmission of digital images without compromising on quality. The first version of the JPEG standard was released in 1992, and it quickly became a popular choice for image compression due to its ability to significantly reduce file sizes while maintaining acceptable image quality.

When to Use JPG

JPG is a versatile image format, well-suited for various scenarios where specific considerations come into play. Here are some situations when using JPG is advantageous:

1. Photographs and Realistic Images: JPG excels at compressing photographs and images with complex color variations, gradients, and fine details. It can maintain a good balance between image quality and file size, making it ideal for storing and sharing digital photographs.
2. Web Images and Social Media: For web developers and social media enthusiasts, JPG is a preferred format for displaying images on websites and sharing them on social media platforms. Its efficient compression helps to reduce loading times, ensuring a smoother browsing experience. However, this position is being challeneged by new formats such as Google's own WebP, which offer compression methods that result in even smaller image file sizes.
3. Large Image Galleries: When dealing with a large collection of images, such as photo galleries or albums, using JPG can significantly reduce the storage space required without compromising on overall image quality.
4. Email Attachments: JPG's ability to compress images makes it practical for attaching pictures to emails without causing issues with attachment size limits.

When Not to Use JPG

While JPG is a versatile format, there are specific scenarios where it might not b e the best choice. Consider alternative formats in the following situations:

1. Text or Graphics with Sharp Edges: JPG's lossy compression can lead to noticeable artifacts around text and graphics with sharp edges. In such cases, consider using PNG or GIF formats, which are better suited for preserving the sharpness and clarity of these elements.
2. Repetitive Patterns or Simple Graphics: Images with repetitive patterns or simple graphics might not compress well with JPG, resulting in larger file sizes than necessary. Consider using PNG or other lossless formats for such images to maintain optimal quality.
3. Professional Printing: When preparing images for professional printing, such as brochures or posters, opt for lossless formats like TIFF or RAW. These formats ensure maximum image quality and retain all the original data without any compression loss.
4. Editing and Repeated Saving: If you plan to edit an image multiple times or apply changes to it, avoid saving it repeatedly as a JPG. The compression process in JPG is lossy, and each time you save the image, you lose additional details and degrade the quality.

Remember that choosing the right image format depends on the specific requirements of your project or use case. Understanding the strengths and limitations of JPG can help you make informed decisions and optimize your image files effectively.

Optimizing JPG Filesize

To optimize JPG file sizes while maintaining acceptable quality, you can use image compression tools or software. In-depth tips and techniques for reducing image file sizes can be found in our comprehensive guide, How to Reduce Image File Size. This guide covers various methods, including image compression, resolution adjustments, and other helpful tricks to make your JPG files more efficient without compromising on visual appeal.

Frequently asked questions about JPG images

What is a JPEG?

JPEG stands for Joint Photographic Experts Group, which is a widely used image file format that uses lossy compression to reduce file size while maintaining reasonable image quality. It is commonly used for storing photographs and other complex images on computers and the internet.

What does JPG stand for?

JPG, or JPEG, stands for Joint Photographic Experts Group. It is a widely known and utilized image file format, serving as an alternative to other formats like PNG (Portable Network Graphics) and GIF (Graphics Interchange Format). Developed by the Joint Photographic Experts Group in the late 1980s, JPG was created to establish a standard for image compression. This standard allows for efficient storage and transmission of digital images while balancing image quality and file size through its lossy compression technique.

What is the difference between JPEG and JPG?

There is no difference between JPEG and JPG. Both terms refer to the same image file format. "JPEG" is the most common extension used on Windows and other operating systems, while "JPG" is the shortened version of the same format.

How to make a JPEG smaller?

To make a JPEG smaller, you can use image compression tools or software that allow you to reduce its quality or resolution. Additionally, you can use online image compressors to shrink the file size without losing much image quality. This guide on how to reduce image file size covers both the tools and steps to make your JPEG file smaller.

How to convert HEIC to JPG?

• On Mac: Use the "Preview" app. Open the HEIC file, click "File," then "Export," and choose "JPEG" as the format.
• On PC: Use an online converter or download a software that supports HEIC to JPG conversion such as Photopea, or Canva's free image converter that supports HEIC to JPG.

How do I change iPhone camera from HEIC to JPG?

Go to "Settings," then "Camera," then "Formats," and choose "Most Compatible" to take photos in JPG format. To convert any existing HEIC photos, upload your photos to a computer and use an online converter or image editor like Canva's free image converter that supports HEIC to JPG.

How to convert WEBP to JPG?

Use an online converter or image editor like Photopea, or Canva's free image converter that supports WEBP to JPG conversion. Upload the WEBP file, select "JPG" as the output format, and convert the image.

How to convert PNG to JPG?

Use an online converter or image editor that supports PNG to JPG conversion. Upload the PNG file, choose "JPG" as the output format, and convert the image. Need recommendations on what tool to use? Further down in this article we've put together a list of online tools for working with JPG files.

Keep in mind there might be a reason your file is a PNG. PNG is ideal for images that require transparency or have simple graphics, such as logos and icons.

How to convert TIFF to JPG?

Use an online converter or image editor that supports TIFF to JPG conversion. Upload the TIFF file, choose "JPG" as the output format, and convert the image. However before you convert - make sure that you save your TIFF-file, TIFF is a high quality format generally used by photographers to retain all of the original image quality.

How to save a PDF as a JPEG?

Use an online converter or image editor that supports PDF to JPG conversion. Upload the PDF file, choose "JPG" as the output format, and convert the image. PDF is ideal for text documents, and in many cases it might actually be a better option than JPEG if your file is a text document. So before you covnert - consider if you couldn't simply use the PDF file instead.

How to save a JPEG as a PDF?

Use an online converter or image editor that supports JPG to PDF conversion. Upload the JPG or JPEG file, choose "PDF" as the output format, and convert the image.

How to save a picture as a JPEG?

• On Mac: You can use the "Preview" app. Open the image file, click "File," then "Export," and choose "JPEG" as the format.
• On PC: Use your preferred online converter or image editor like Photopea, or Canva's free image converter that supports conversion from your current picture format to JPEG.

How to save a Word doc as JPEG?

The quickest way to save a Word document as a JPEG is by taking a screenshot of the document and then saving it as a JPEG image. Press "Print Screen" (PrtScn) on Windows or use the screenshot shortcut on Mac (Shift + Command + 4), paste it into an image editing software, crop if needed, and save as JPEG.

If a screenshot is not enough, consider exporting the document as a PDF (which in many cases will work just as well as a JPG or JPEG). If you really need a JPG file, you can then convert the PDF to a JPEG using online converter tools.

How to reduce the size of a JPEG?

Use an image compression tool or software to reduce the quality or resolution of the JPEG. Alternatively, use online image compressors to reduce the file size without significant loss of image quality. Check out this guide on how to reduce image file size for more ways to reduce the size of your JPEG.

How to edit a JPEG?

Open the JPEG in an image editing software such as Photoshop, GIMP, Paint.NET, or Photopea. Edit the image as desired, then save the changes. Keep in mind that repeated editing and saving of a JPEG can lead to a loss in image quality due to the format's compression.

Online tools for working with JPG files

Image editors for JPGs

• Adobe Photoshop: A powerful and widely used professional image editing software with a broad range of features and tools.
• Photopea: An online image editor that supports various file formats, including JPGs, providing many Photoshop-like features.
• GIMP: A free and open-source image editing software with capabilities similar to Adobe Photoshop.
• Paint.NET: A user-friendly image editing software for Windows, offering essential editing features.

Conversion tools for JPGs

• Canva Image Converter: Canva's tool for converting images to different formats, including JPGs.
• Adobe Express Convert tool: Adobe's online tool to quickly convert images to JPG format.
• IMG2GO Image to Image converter: A web-based converter for various image formats, including JPG.

Compression tools for JPGs

• TinyPNG: Specifically designed for PNG and JPEG compression, TinyPNG produces impressive results for both photographs and graphics.
• ImageOptim: A versatile tool that supports various image formats and provides excellent compression without compromising quality.
• Compressor.io: This platform offers multiple compression options and lets you see how different settings affect the image quality.

Cropping and resizing tools for JPGs

• ImageResize.ai: Our AI-powered tool to extend, resize, and crop images to the most common formats and ratios.
• Adobe Free Image Cropper: A tool to crop larger images into smaller sizes.
• Canva Crop Image: Canva's feature for easily cropping images to specific dimensions.

How The JPG Format Compresses Your Image

If you are knee-deep in image-nerdery like me, and want to find out the inner workings of the JPG-format, here's a section dedicated to you:

JPEG compression employs a sophisticated algorithm to achieve its impressive image compression while maintaining an acceptable level of visual quality. Here's a breakdown of the key steps in the JPG compression process:

1. Discrete Cosine Transform (DCT): The compression starts with dividing the image into small, square blocks known as "8x8 pixel blocks." Each block represents a section of the image. The DCT is then applied to these blocks, converting the pixel values into frequency domain coefficients. The DCT essentially identifies the frequency components of the image, helping to concentrate the image data in the lower-frequency coefficients.
2. Quantization: After the DCT, the frequency domain coefficients are quantized. This step involves dividing the coefficients by specific values called "quantization tables." The quantization process allows reducing the amount of data significantly. The higher the compression level, the more aggressive the quantization, leading to greater data reduction but also increased loss of image detail.
3. Chroma Subsampling: JPG often uses a process called "chroma subsampling" to further decrease file size. This means reducing the color information (chroma) while preserving the brightness (luma) data. The most common chroma subsampling ratio used is 4:2:0, which means that for every four luma pixels, there are two chroma pixels in both the horizontal and vertical directions. Chroma subsampling can introduce some visual artifacts, especially in images with sharp color transitions.
4. Huffman Encoding: The quantized coefficients are then run through Huffman encoding, a variable-length coding technique. This encoding assigns shorter codes to more frequently occurring values and longer codes to less frequent values. Huffman encoding is particularly efficient for compressing the quantized coefficients, resulting in further reduction of data size.

JPG Compression Quality and Artifacts

The balance between compression level and image quality is a crucial factor when working with JPG. Higher compression levels lead to smaller file sizes but at the cost of increased image degradation and visible artifacts. Here are some common artifacts associated with JPG compression:

• Block Artifacts: Aggressive compression can cause blocky artifacts, especially in areas with abrupt changes in color or brightness. These artifacts are a result of the 8x8 pixel block processing and quantization.
• Compression Artifacts: Overly compressed images may exhibit compression artifacts, such as "blocking" or "mosquito noise," where small, random squares or distortions appear around edges and fine details.
• Color Banding: Heavy compression can lead to color banding, where smooth gradients are reduced to distinct bands of colors, resulting in a loss of color smoothness.

Lossless vs. Lossy Compression

JPG uses a lossy compression method, which means that some image data is permanently discarded during compression. This contrasts with lossless compression formats like PNG, where no image data is lost. The choice between lossy and lossless compression depends on the intended use and the importance of maintaining image quality.

While lossy compression significantly reduces file sizes, it is not recommended for situations where image fidelity is critical, such as professional printing or preserving original artwork.

This JPG-guide is part of an article series

Thank you for reading this far! Now that you know almost everything that is worth knowing about the JPG/JPEG format, check out the other parts of this article series: PNG, HEIC, GIF and WEBP.