Image Formats and File Size
Image file size
When images are used extensively in a course, it is important to consider their file size. In general, the larger the image and the higher its quality, the larger the file will be. A large image file can make a web page take longer to load and display for the user.
If images are compressed before they are published on the web or in Canvas, they load more quickly. Reasonable compression does not degrade the image’s visible quality. See Cropping and compressing an image.
Images published on a course site are stored in the course files. The course file storage limit is 4.2 GB, which should be more than enough if files are managed appropriately.
Image formats
The most common image formats are JPG, PNG, GIF, and SVG.
JPG – In most cases, photographs should be saved in JPG format.
PNG – Graphic images with clean, solid colour areas are usually best saved as PNG files.
SVG – In SVG (Scalable Vector Graphics) format, the size of the image is controlled by vector calculations. This means the image can be enlarged or reduced without losing sharpness. SVG format is used, for example, for diagrams and maps intended for web display.
Choosing the right image format can affect an image’s file size. See more in the section on cropping and compressing images.
Reducing the file size of images in a PowerPoint presentation
Students may have difficulty opening presentations that contain many large image files. Even if the presentation opens without problems for the teacher, it may not for other users, as technical conditions can vary.
By compressing the images, the presentation becomes smaller and takes up less space in the course files. If this is done correctly, there is no visible difference in image quality.
PowerPoint lets you compress all images in a slide presentation for web use in a single step. See Microsoft’s instructions: Reduce the file size of your PowerPoint presentations.
Save as PDF
If a PowerPoint presentation is saved as a PDF, the PDF file may become smaller, especially if Minimum size is selected when saving. However, this does not replace compressing images in PowerPoint, especially if the PowerPoint file itself will be shared. It is best to compress the images in the presentation before uploading it to Canvas or saving it as a PDF.