An image post format in WordPress is used to display a single image or photograph.
Images come in several different types, and each has a use. Some of the file suffixes you’ll run into are JPEG, TIFF, PSD, BMP, PICT, and PNG.
Here are some general guidelines for the uses of each kind of image file:
- If the images are for web or mobile, use JPEG, PNG, or GIF.
- If the images are to appear in printed material, use TIFF.
- If you want to keep a version that remains editable, choose your software’s native file format such as PSD for Photoshop,
When to Use JPEG
Joint Photographic Experts Group (JPEG or JPG) is best for photos when you need to keep the file size small and don’t mind giving up some quality for a significant reduction in size.
When a JPEG file originates, the compressor looks at the image, identifies areas of common color, and uses them instead. Colors the compressor doesn’t identify as common are “lost.” The amount of color information in the image reduces, which also reduces the file size.
You usually set a quality value for a JPG like the Photoshop Image options, which have values from 0 to 12. Anything below 5 will most likely result in a pixelated image because the compressor throws out a vast amount of information to reduce the file size. It’s better to try for a quality value of 8 or higher. JPEG is not suitable for images with text, large blocks of color, or simple shapes because crisp lines will blur, and colors can shift.
The three types of JPEG are Baseline, Baseline Optimized, and Progressive.
- Baseline (Standard) – All web browsers recognize this JPEG format.
- Baseline Optimized – This JPEG format option provides an optimized color and slightly better compression. All modern browsers support it, but earlier ones didn’t. It’s your best choice for JPEG files today.
- Progressive – Creates a JPEG file that displays as it downloads, starting blocky, and getting progressively clearer as it downloads. It doesn’t make the image download any faster, but it can give the illusion of speed since the blocky image loads right away on a slow connection. With the majority of internet users on high-speed connections today, Progressive JPEG is rarely used.
When to Use TIFF
TIFF (Tagged Image File Format) is suitable for any type of bitmap (pixel-based) images destined for print because this format uses that industry’s CMYK color standard. TIFF produces large files, thanks to a common resolution of 300 ppi with no quality loss. TIFF also preserves layers, alpha transparency, and other special features when saved from Photoshop. The type of extra information stored with TIFF files varies in different Photoshop versions, so consult Photoshop’s help for more details.
When to Use PSD
PSD is Photoshop’s native format. Use PSD when you need to preserve layers, transparency, adjustment layers, masks, clipping paths, layer styles, blending modes, vector text, and shapes.
Only Photoshop can open and edit PSD files, but some image editors will open them.
When to Use BMP
Use BMP for any type of bitmap (pixel-based) images. BMPs are huge files, but they have no loss in quality. BMP has no real benefits over TIFF, except that you can use it for Windows wallpaper. BMP is an image format left over from the early days of computer graphics and doesn’t receive much use anymore.
When to Use PNG
Use PNG when you need smaller file sizes with no loss in quality. PNG files are usually smaller than TIFF images. PNG also supports alpha transparency (soft edges) and started as a web graphics replacement for GIF.
To retain full transparency, save a PNG file as PNG-24 and not PNG-8. PNG-8 is useful for reducing file size when you don’t need transparency, but it has the same color palette limitations as GIF files.
The PNG format also commonly appears in images for iPhones and iPads. Photos don’t render all that well in the PNG format. It’s a lossless format, meaning they aren’t compressed and have significantly larger files sizes than their JPG cousins.
When to Use GIF
Use GIF for simple web graphics having limited — up to 256 — colors. GIF files make small, fast-loading graphics for the web. GIF is great for web buttons, charts or diagrams, cartoon-like drawing, banners, and text headings. People also use GIFs for small, compact web animations. GIF should rarely be used for photos though there is a resurgence of GIF images and GIF animations thanks to the rise of mobile devices and social media.