Media compression

PNG (Portable Network Graphics) images have a ".png" file extension, and are considered a "lossless" image format. This means that a compressed PNG image does not reduce in quality, and is best used with "graphics" that contain contiguous areas of the same colour. PNG images also support alpha transparency.

Photos, and images with photo images should not be used with PNG because it cannot be efficiently compressed.

For example, the following graphic as a full colour PNG is 125KB:

In comparison, the following photo at the same size, as a full colour PNG is 353KB:

PNG images can be made smaller by reducing the number of colours. For example, the above photo reduced to 256 colours using a standard palette is now 57KB:

This method visibly reduces the quality of the image. Another method is called "quantisation", which reduces the number of colours based on which colours are most used in the image. This image is reduced to 256 colours, which is also dithered to enhance blending and is now 119KB:

The quality of the image is reduced, but not perceptably. On displays like LED signs, this is almost undetectable.

When PNG images are compressed by Remote CMS, this is the method that is used.

JPEG (Joint Photographic Experts Group) images have a ".jpg", ".jfif" or ".jpeg" file extension, and are considered a "lossy" image format, specialised for digital photos. This means that a compressed JPEG reduces the image quality by removing the 'least important' details such as photo grain and noise while keeping the 'most important' details of the photo. A JPEG compression ratio (or "quality") can be adjusted from 0% to 100%, where 0% is the most heavily compressed and 100% is not compressed at all. JPEG images do not support transparency.

For example, the following photo at 100% quality (no compression) is 277KB, which is notably smaller than the uncompressed PNG image.

Saving the same photo as a 10% quality JPEG reduces the file size to 24KB, but the image quality has been greatly reduced. "Artifacts" have been introduced, which appear as blocky sections or distortions around the edges of the image.

Saving the original photo as a 70% quality JPEG reduces the file size to 55KB, and the image quality is imperceptably reduced. Distortions still appear, but are minor.

When JPEG images are compressed by Remote CMS, the image is compressed at 70% quality.

GIF (Graphic Interchange Format) images are an older media format that only supports 256 colours, 1-bit transparency (each pixel can either be completely transparent or completely opaque). GIFs may be animated, and are suited to small graphic animations.

For example, the following animated GIF image is a simple graphic with 24 frames in total and is 23KB:

This format is not well suited for very large images, animations with extended durations, or video content. For example, this short video clip is 320x240 like the previous animated GIF but the file size is 2.17MB.

GIF animations do not have any compression options for Remote CMS.

Remote CMS supports MP4 video files encoded with the h264 codec (this is the native format of many sites such as YouTube). MP4 videos can be uploaded with any RemoteCMS account, but they can only be used with compatible display devices. Video files can be encoded with a number of configurable properties such as width, height, bitrate, quality etc. Depending on the selected configuration the video file can become quite large.

Remote CMS does not offer a compression or encoding service. Care should be taken to reduce the size of video files before uploading them to RemoteCMS.