In risr/assess you can add images, videos, sound clips and documents to Items to provide further information, context, question content or otherwise. We use the term Resources to collectively refer to these extra pieces of information.
Resource Types
Resource Type | Summary |
|---|---|
Written document which can include images. Can be Candidate or Examiner instructions, marking criteria, case studies, scenarios, etc. | |
Audio | An audio clip |
Video | A video clip |
Image | A static image |
DICOM | Grayscale or Colour are supported, as are different types of multi-slice DICOM. |
Summary of Recommendations
Images come in a variety of file formats, some are recommended and supported, however there are some that we do not recommend or do not support for use in your exam.
The exact image type will depend on a few factors about how it may be used in a question. Key considerations are:
Will the user need to look in detail at the content? E.g. graphs or scan content for inspection.
Is it necessary to zoom in on the image?
Download speed / size
How is the image presented? E.g. method used for taking the exam, paper/device screen
It may be that your source image will need to be optimised to align with the above considerations. The following is an outline of the suggested optimisations when determining the image file you are going to use in your exam.
Compression
Refers to file size
Compressing images helps to reduce the file size which aids in your upload and download speed. All files will have a variable download speed depending on each user’s device capability and internet access. For an exam image, it is important to reduce the file size so when the encrypted file is downloaded onto the user's device, it will download quickly. You do however need to be mindful that if you compress images too much, they will lose their quality and can become blurry (a form of pixilation).
Pixel Dimensions
Refers to size of image in pixels, x and y dimensions i.e. how many dots make up the picture. Different outputs will display a varying number of pixels per inch/centimetre
When you compress a file, you may reduce the quality but still keep the same number of pixels, however you are likely to lose detail in what is shown. The more pixels you have, the larger the file size. Reducing the pixel size of an image is a fast way to increase the upload/download speed. This however leads to a reduction in quality, changing the image quality from being clear to blocky (another form of pixilation) on the screen.
Aspect Ratio
Refers to the proportion of width to height
Changing both, or either, the width and height will change the proportion of the image, if not properly done this will distort the image. You may choose to crop an image for an exam to remove some of the negative space, by doing this you may change the aspect ratio and unintentionally emphasise an area of the image. As a guide a HD TV image has dimensions of 1920 x 1080 (width by height).
Resolution
Refers to quality
Often measured in dpi (dots per inch) this is independent of the dimensions of the image, but can affect the display size. 300dpi is a generally accepted measurement for maintaining image quality, especially for print, or enabling zoom on an online image. This can be reduced for web viewing to as low as 72dpi for screen display, but at this scale zooming will not be effective. An image with high resolution may allow you to zoom in for better detail, but will have a bigger file size.
Recommended and Supported Image File Types
File Type | Recommended | Supported |
|---|---|---|
PNG | ✅ | ✅ |
JPEG | ✅ | ✅ |
DICOM | ✅ | ✅ |
mp4 | ✅ | ✅ |
❌ | ✅ | |
TIFF | ❌ | ✅ |
GIF | ❌ | ❌ |
HEIC | ❌ | ❌ |
PNG
This type of image is best used for graphical images. This file type can have a transparent background where necessary.
JPEG
These file types files are compressed image files, and ideal for photographic images. When saving JPEG files in any image editor you may have options on a quality scale from low to high. This results in a compromise in quality vs file size.
TIFF (TIF)
This file type is generally uncompressed and therefore is often large in size (often 4-10 times larger than a jpeg equivalent). These large file sizes also significantly increase the time to upload (during exam preparation) and download (impacting the user experience during an exam). You may want to keep these as a reference or master resource and create a good quality JPEG version for use in an exam. Because of the size issue, these file types are not recommended and appear with a warning when creating the Resource in DRAFT state and when viewing in the Resource Library.
DICOM
DICOM images are multi slice images that are highlighly compressed but produce a quality multislice image. The file sizes are large and best used to display X-Rays, CT Scans, etc.
More information on supporting the use of dicom images on Practique can be found on Dicom Image support and Uploading Dicom images.
PDF files are usually document files but can be used for images, though this is not recommended for use in Practique. The image in a pdf is often embedded as one of the other formats described above.
HEIC
HEIC file type is an Apple specific format found on mobile devices. It saves images in a high quality using advanced compression. These are currently not supported in Practique.
GIF
This file type is useful for moving images with a repeating motion, online images, logos and are compatible with some online platforms and are used for web display. However, they are not supported in Practique.