Following digitisation you may find that some images require manipulation. This stage can be as simple as cutting out a border, however, you may allocate more time to this stage to make finer adjustments such as exposure or colour edits. This section offers advice and guidelines on common techniques.
Always try to get the best possible image at the point of capture. In a digital preservation workflow, ideally you shouldn't have to do anything to it other than enter it into a preservation management system.
Before you carry out any form of processing - Save a master copy! This master image should be securely stored and remain untouched. Any work required should be carried out on a surrogate image.
Depending on your project workflow this stage can be done on each scan following capture, or in a batch as a process in itself. Either way, you should perform a quality check first, next decide if and what post processing is needed and finally, do the processing. You should continue to use the spreadsheet from the previous stages, tracking the items throughout the digital preservation process.
The image processing stage is very useful for cleaning up mistakes or compensating for limitations at the capture stage, especially where the condition of an item has meant imaging is difficult.
It can also save resources if you are restricted on time, labour or access to equipment and are working in large batches.
Time - When planning for image processing, you must decide how much work is required and stick to that plan. It is very easy to keep working on an item in pursuit of 'perfection', but that eats into the time available for the remaining project tasks.
Labour - It helps to have the scans checked by someone other than the operator who performed the scans the items as the same issue can be missed a second time.
Finance - You may need to purchase editing software if you find the programmes available to you are not sufficient for the work needed. If you need the images to be 'restored' then you may need to pay a professional to carry out this work.
Equipment - Image editing requires a P.C. or laptop, preferably with a good graphics card. However many software packages are available to use online so downloading to a desktop is not absolutely necessary.
Software - There is a huge selection of software available, from desktop to cloud and ranging in price and difficulty of use. Check out the section on software to find out which ones are best suited to your needs. Look for training videos online to find out how to use the features.
In some cases images can be digitised specifically to edit them and restore or enhance an original. Not all software will allow fine editing and even where it is available, you may need to spend a lot of time to accomplish the task but if it is important to the project goal, you can usually find online training videos to help.
Issues such as fading or over exposure can be improved by adjusting light and dark levels, exposure and contrast.
Marked photographs can be improved by filling the space with the matched colour (paint) or by copying a similar section of the picture and replacing the mark with it (clone).
These are commonly used features for image processing.
Cropping allows you to reduce an image down by removing sections (such as a border or an unwanted visible tool used to position an item for digitisation). It is very useful for separating multiple items scanned in a single image (e.g. photographs stuck on the page of an album).
Cropping will decrease the size of an image but you may need to resize a large image for sharing (e.g. email or publish online). You can do this by decreasing the number of pixels.
While you can make a lower resolution version of an image from a higher resolution one, the opposite is not true so always store a master image of the unedited original.
Even when you use guide or rulers to line up your original, you can still find the image is slightly (or greatly) crooked. Most software allow you to rotate an image to some degree to fix this issue.
The granularity of rotation offered varies depending on the software so check that your package does what you need.
90° clockwise or anticlockwise rotation means you can capture your images sideways which can help if you have landscape items on a portrait scanner, and vice versa.
Arbitrary degrees of rotation are offered by some software. This allows you to turn the image by very small increments.
Horizontal and vertical flipping mean you can flip an image left to right (a mirror image) or up to down, respectively. When scanning negatives without markings to indicate the orientation, you might only find out an image is backwards when you see the scan but a horizontal flip fixes this in one click.
When scanning a tightly bound book you may find the text towards the spine will curve. Look out for the deskew feature on some software.
Some software will automatically do these functions for you when a slanted image is detected.