In the world of digital images, a whole range of different image file types exist. But which image file type is suitable for which purpose? What are the advantages and disadvantages of well-known graphic files such as JPG, PNG or SVG? What is the difference between raster and vector graphics? In this article we answer the questions and give an overview of the most important formats of images.
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Raster Graphics vs. Vector Graphics
A raster graphic consists of pixels arranged in a grid. Each pixel is assigned a specific color value. This allows complex color gradients to be displayed. The color depth indicates how many colors are available for an image. This does not mean the number of colors, but how many bits are used for the color information. The image resolution or image size, on the other hand, indicates how many pixels the image consists of.
Images taken with a smartphone or digital camera are saved as pixel graphics. Raster formats are therefore mainly used for photos.
In contrast, vector graphics do not store image information in pixels. They consist of graphic primitives, such as lines, circles, and other geometric shapes. These can be scaled as desired without any loss of quality.
Vector graphics are often deployed for logos, which are required in different sizes.
The larger a digital image, the more storage space it requires and the longer the transmission time. For this reason, compression is used to reduce the file size. However, the compression may reduce the image quality depending on the file format.
Image and graphic file formats are usually in one of two color models: RGB or CMYK. The RGB color profile is suitable for display on monitors. CMYK, on the other hand, is a prerequisite for four-color printing.
Each image format offers different advantages and disadvantages, which are presented below.
Popular Pixel Formats
JPG (JPEG) - Joint Photographic Experts Group
The JPEG is one of the most common image formats, as it is supported by all operating systems and has a good ratio between image quality and file size. The JPG file format is mainly used for large, detailed images such as photos, as it can reproduce the full spectrum of colors. It supports both the CMYK and RGB color models. Therefore, it can be deployed for saving photos as well as for printing and websites.
However, JPEG files do not support transparency. Animations or a layer display are also not possible. In addition, the compression is lossy: multiple saving and scaling can quickly lead to quality loss.
What is JPEG2000?
JPEG 2000, like JPEG, was published by the Joint Photographic Experts Group. The .jp2 format offers a better compression rate than classic .jpg files and the possibility to add metadata in XML format. However, the format is not widely widespread and is not supported by many programs and web browsers.
Are JPEG and JPG the same thing?
Yes, both terms stand for the same format. The term JPG exists because earlier versions of Windows limited file extensions to only 3 characters. In addition to JPEG/JPG, there are also some sub-file formats such as JFIF.
PNG -Portable Network Graphics
In contrast to the JPG image format, PNG is a raster graphics format with lossless data compression. It also supports transparency (also with gradations) via alpha channel. The PNG format is therefore well suited for icons, transparent and semi-transparent areas in images or logos on websites.
Since it does not support CMYK color model it is not suitable for printing. For the use of PNG images in the online area, it should be noted that the files can be significantly larger than JPG files, if, for example, detailed photos are saved in this format and not further compressed.
GIF - Graphics Interchange Format
The GIF image file type is mainly known as an animation format because several single images can be stored in one file. Unlike JPG or PNG, GIFs only have a color range of 256 colors. Thus, the GIF format has a lower color depth and is therefore less suitable for photos with a wide spectrum of colors. The GIF format enables lossless compression and allows transparency. It supports animation and also has acceptable small file size. Therefore GIF files have short loading times and are mainly deployed for animated images.
Originally, the GIF image format was mainly used on website banners. Today, GIF animations are used especially in social media like Facebook or Whatsapp, for example to express emotions.
TIFF - Tagged Image File Format
The TIFF format supports the CMYK color model. It can store layers and allows transparencies. Since it is usually not compressed, it is not lossy. TIFF files are mostly deployed as print data. Especially in the pre-press stage in publishing and printing houses, TIFF is often used.
Due to its high quality, however, TIFF also has a very large memory requirement. The TIFF format is therefore not suitable for use on websites, also because it is not supported by many web browsers.
PSD – Photoshop Document
The file format of Adobe Photoshop offers the advantage of extensive editing of image layers. All image information is stored lossless, accordingly the file size is very large. An Adobe Photoshop license is required to open and edit the file. The format has low compatibility but can be converted directly to other formats (raster and vector graphics). It is also possible to create animations and videos. The PSD file type is a format that is only used in image editing.
The WebP image format was introduced in 2010 by the Google search engine to speed up website loading times. WebP achieves better image quality than a JPG file when compressed to a very high level and, like PNG, offers the possibility of transparencies. It allows both lossless and lossy compression and is suitable for photos as well as for small images and illustrations. The format is supported by almost all modern web browsers and can greatly reduce the loading time of websites. Google therefore recommends the use of this format for web pages. However, older browsers have problems displaying the format.
RAW (CR2, CRW, NEF, PEF, ORF, …) - Raw image format
The raw data format is the image format in which a digital camera saves the photos. It depends on the camera manufacturer and partly differs from camera model to camera model. There is no uniform raw data standard.
All formats offer a high degree of flexibility for image processing but require a lot of memory and are not very compatible. For this reason, raw data formats such as CR2, CRW, NEF, PEF or ORF are further processed and saved in the appropriate format depending on the intended use. The raw files are usually supplemented by the camera with further data, for example EXIF metadata or a preview image in JPEG format.
BMP – Windows Bitmap
The image format introduced by Microsoft in 1990 is hardly used today, because it has a very large file size compared to other image formats. It can represent a large color spectrum and is still an integral part of Windows, for example in the clipboard. However, it is not supported by web browsers.
HEIF - High Efficiency Image Format
HEIF or HEIC is a flexible file format for images and image sequences that supports various compression options. As a result, it requires only half the storage space of a JPG image with the same image quality. Apple introduced the format and iPhones save their photos in this format by default since iOS 11. However, other systems do not support the format. Therefore, when images are distributed via social networks or transferred to Windows PCs, for example, they are automatically converted to the JPEG format.
Popular Vector Formats
SVG - Scalable Vector Graphics
The SVG format offers high quality, lossless scaling and is therefore ideal for responsive design. It is supported by most web browsers and is suitable for web pages as well as for print, or logos. The file size is small but can increase quickly if the graphics are complex and detailed. In addition, special software is needed to edit the file. Within Adobe Creative Cloud, this is only possible with Illustrator.
EPS - Encapsulated PostScript
The format was introduced by Adobe back in 1987 and is compatible with almost any design software. It is particularly suitable for high-resolution graphics and illustrations for printing. However, it has been largely superseded by the PDF format because it does not distinguish between vector and bitmap.
PDF - Portable Document Format
The PDF format is considered the standard for print data. It is platform-independent and no paid software is needed to display it. Text can be recognized as an image in PDF. Partly the format has high memory requirements, but it also offers some additional functions. For example, PDFs can contain buttons, links or even audio and video elements.
AI – Adobe Illustrator
As the name suggests, Adobe Illustrator is a prerequisite for this highly scalable file format, which is also compatible with other Adobe programs. It can have multiple image layers and therefore requires a lot of storage space. The AI graphics format - similar to the PSD format - is a classic working file used for editing graphics. The result is saved out in the appropriate format at the end.
CDR - CorelDraw
CDR is a vector graphics format developed by Corel Corporation. CorelDraw Graphics Suite is especially widely used on Windows systems. It is the standard format for Corel Draw applications and is recognized by most other image editing programs.
WMF - Windows Metafile or EMF - Windows Enhanced Metafile
EMF is the further development of the WMF format from Microsoft. It was developed for the exchange of graphics between illustration programs and Microsoft Office applications. The further development EMF has a greater color depth than the predecessor format. The format is mainly used for exchange between programs.
Digital asset management software helps you stay on top of things
This article has provided an overview of popular image formats. To keep track of their image files in the company, the use of a digital asset management solution is recommended. Here you can store all image formats centrally, enrich them with metadata, organize them better and retrieve them faster. A digital asset management system can also handle converting files to another format for you and generate previews of all file formats without requiring each user to have the appropriate program installed.