How to remove noise from scanned documents
Why do unwanted dots and marks appear on the document?
Anyone who often scans documents probably knows the problem: The digital copy contains annoying dots or marks. How can these be removed or prevented afterwards or during the scanning process? The first step is to find out how the noise came about. This way, future scans can be improved and do not have to be edited afterwards.
Often, Impurities occurs inside the scanner device. Especially on the glass of the scan unit, small lint or debris can accumulate over time, which are responsible for the problem. Before software is used to remove impurities, it is worthwhile to have the glass professionally cleaned.
However, sometimes you scan a copy that already has dots and marks printed on the paper. In this case, post-processing is necessary to remove them. How this works with a free software, we explain in the next section.
Removing noise from scanned documents using free software
Our free document management software bitfarm-Archiv offers tools for graphics editing in addition to many other features. Among them is the possibility to remove unwanted dots or stripes. The procedure is as follows:
- Archive the document
- Select the document
- Take the document into the editing mode (F2)
Under "Graphic" select "Remove single dots".
Select the pixel thickness with which the points are to be removed
Detailed instructions: In the first step, archive your document to the storage or archive you have chosen. Then call up the document. To do this, you can either open the corresponding warehouse or use the search function. After you have clicked on the document in the hit list, set it to the edit mode.
To start the mode, you can either press the F2 key or the "Edit" button. If there is a green frame in the preview view, the corresponding mode has been selected successfully. Now select the "Graphic" tab. There you will find the submenu "Remove single dots". After you have selected this function, you will be asked which dots should be removed. This is defined by means of the pixel thickness.
Here you can select points up to a thickness of 4 pixels. There are no universal presets here, so you will have to test which option suits your document best. If they are not satisfied with a selection, they can always select the "Cancel" button. This will undo the changes. This also deactivates the edit mode at the same time.
What else can be considered?
Our software usually recognizes the points very accurately, but this requires that the correct pixel size has been selected beforehand. In case the result is still not as desired, the following tips can be considered:
- Use a high resolution scan (High DPI)
- Replace the scanner if cleaning does not help
- Use free photo editing tools like GIMP
- Ask the originator of the original document if they can send you a cleaned up copy
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