The Image Compression tab is the second tab in the Publish Options dialog and deals with how images are compressed when your publication is published. Opus uses JPEG compression to reduce the size of the image files of your publication but this is a lossy compression technique which means that detail may be lost if the compression is too high.
Note:
By default Opus uses a compression level that will be unnoticeable in most instances. However, the Image Compression tab is available to change the image compression settings in either direction for the selected resources.
The Image Compression tab is part of the Publish Options dialog – you must select the resources in the Resource pane of the Resource Manager window before you fill-in the Image Compression tab settings – see Publish Options for more information.
The Use the settings from the parent folder option is the default setting for this tab. This means that the publishing settings are the same as the folder immediately above them in the Organiser in the Resource Manager window. If none of the folders that contain resources for this publication are given different publishing settings then the default settings are applied.
Use the Use Default Image Compression Settings option if you want the selected resources to use the same settings as the default settings when the publication is published.
Use the Disable Image Compression option if you do NOT want to compress the images at all.
Use the Enable Image Compression option if you want to change the image compression for the selected resources – choosing this option will enable the Compression Options panel.
Use the Use Lossless Compression only option in the Compression Options panel if you want to switch the JPG compression off and use a compression technique that does not have the potential to reduce the images detail.
Note:
This will most likely increase the file size of your publication.
Use the Reduce to 32K colours option in the Compression Options panel if you want lower the colour depth of the images to 32K colours.
Use the Use dither option in the Compression Options panel if you have reduced the images to 32K and they look a bit blocky.
Note:
Dithering is a process of constructing the colour of one pixel from its surrounding pixels to make the images less blocky – however, your image may still look a bit speckled in appearance.
Use the Use JPEG Compression option in the Compression Options panel if you do want to use the JPEG compression method but want to change the level of compression. Use the spin buttons to increase or decrease the level of compression. The lower the compression, the most likely the quality of the image will improve. By default, the Quality is set to 75%, which in most cases is an optimum setting.
The Enable Image Resizing option is available for whichever compression method you have previously selected in the Compression Options panel. This option allows an image to be resized from its original size in your publication. By default, this option is ticked.
Note:
You may resize an image in your publication by stretching it in an image as an interesting visual effect.
Click on the Apply button at the bottom of the Publish Options dialog to save your changes.
File Locations Settings - Resource Manager
File Compression Settings - Resource Manager