batch correction of pixel-size errors in lines (1-bit images)

Question

I have 1000 1-bit images that feature lines of ~20 pixels width. However, there are sometimes small 1-pixel holes and frayed bits which create an issue when I vectorize the lines in a Geographic Information system. I attach 2 screenshots to show how this creates a problem in the vectorization.

So, I'd need to blur the image or smooth it some way that these 1-pixel gaps are filled without changing the image size. And I'm looking for a batch process because doing this by hand over 1000 times is not in my plans. I do have Photoshop and IrfanView installed.

I tried to blur and compress the images, but it was no good.

As per request, the result should look like this:

.

Answer 1

I assume that your 1-bit images are not scaled like the ones you post where each block is 10 pixels wide. I've taken one of your screenshots, scaled it down so every pixel is 1:1 and added a little more noise to remove.

I propose the following method in Photoshop:

1. Convert the image from Bitmap mode to either Grayscale or RGB (to enable the use of filters).
2. Choose Filter > Noise > Dust & Scratches.
3. Set Radius to the wanted amount of smoothing.
4. Press OK.
5. Optionally convert the image back to Bitmap mode.

Answer 2

I thought it could be fun to make a Photoshop action for that. You can probably achieve this in different ways, here's what I did:

• action first increases height of the canvas by 200px: this will be required for cases when red pixels touch top or bottom because I'm going to manipulate selections;
• then it uses Magic Wand with 0 tolerance to select whites; inverts the selection; fills it with red and creates a new layer from selection: now I have all the red parts as a separate layer:

• now action copies this base layer 4 times, each time moving it 5px down. The idea here is that top part of my duplicates now should overlap top part of the original layer. Here I made it black to undertsand it easier:

• I obviously don't need the bottom part, so I load selection from the original layer, move it 40 pixels to bottom and clear selection:

• now the action does the same for bottom part: several copies, load selection from original layer and move it, clear. The last part is to change the canvas back to original -200px size.

Result:

Action: https://www.dropbox.com/s/rmy4ug80xyh9u71/Set%202.atn?dl=1

Add a Save step to the action and it could be used in Batch (File > Automate > Batch)