This is the process I use to digitize a drawing I make to publish in a book.
Draw with mechanical pencil and outline it with a Sharpie.
I erase the pencil lines and scan the finished drawing.
I open the scanned document on a free picture manipulation program called Gimp.
Click on File and Open as Layers.
Open the image where you saved it. Mine is saved on my desktop as drawing.
Change the resolution from 100.00 pixels/inch to 400.00 pixels/inch. Then click import.
Then your image will appear on the screen.
If you want to turn the image, select Image on the toolbar, transform and select in which direction you would like to rotate the image. I’m rotating 90 degrees clockwise.
If your picture is not straight, you can rotate it with the rotate tool. Select the tool and click on your picture. Click the up arrow or the down arrow next to the angle to rotate the image up or down. When you are happy with it click rotate.
Select the colour picker tool and zoom into the image. Click on a black line and it should vibrate.
Zoom out and select a white area of the picture. The picture will still be vibrating, but it looks slightly different and then press the delete key on your keyboard.
This will delete all the white areas from your picture and you will be left with a black outline on a grey checkerboard background.
Click on Select and then none. Your image will stop vibrating.
Click on the page icon found on the bottom right side of your screen.
A create a new layer box will pop up. Select white under layer fill type and click ok.
The white layer will be on top and cover your picture on the bottom. Drag the blank layer down and your drawing will be on top.
Select file, export as and click. Rename your file to png and click export. I would suggest saving it to your desktop for easy access. You may close the Gimp program.
Go to your desktop and drag the png image over the Inkscape icon to open it with inkscape. Select embed and click ok.
The image will be opened with Inkscape.
Click the select tool and click on your image. It will be surrounded by black arrows.
Click path and trace Bitmap. Select grays and update. Your image will look a bit warped, but don’t worry. Click ok.
Click the select arrow again and hover over your image. A hand icon will appear. Click and drag your image to the right. You will notice that there are two images.
If you zoom into the images you will notice the one on the left is rougher than the one on the right. Click the select arrow and select the image on the left. Click delete and you will be left with one image.
Click file, export bitmap. Change the name and export as a png.
Open Gimp again. Select file, open as layers and open your new saved image from your desktop.
Select the colour picker tool and select a black line from your drawing. The image will vibrate.
Click edit copy, then edit paste as and select new layer.
A new layer will be placed on top of your previous layer and double vibrating lines will appear.
Click on the eye icon to hide the bottom layer. Only the top layer will be visible.
Click select, none and the image will stop vibrating.
Now comes the fun bit. Select the paint bucket and click on the black lines to define them.
Click the foreground colour box, select your colour and click ok. Click on the area that you want to colour.
Repeat this step for all of the colours you want to add to your picture.
If you have clicked an area and the colour ‘bleeds’; don’t panic, just CTRL Z to undo it. The colour bleeds because the drawing isn’t closed off. If you zoom in you will be able to see that it is not connected to the edge.
Click the pencil tool. Make sure your colour is set to black. Click brush and select your brush type. To increase your brush size, click the up arrow next to the word size.
Draw the lines to close the image and you can continue colouring with bucket fill.
If you aren’t sure which colour to use, you can import an image saved on your pc and pick the colours from the image and incorporate it into your picture. Click file, open as layers, choose your image and open.
The image will be on top of the image you are busy colouring. Select the dropper tool. Click on the colour you want to use and it will appear in the colour box. Make sure you are on the top layer so that you select a colour from the image you just imported. To hide the top layer click on the eye icon and it will disappear from view. Click on the layer below the top layer to work on it again.
When you are finished colouring the picture, zoom into the image to check that you coloured all areas. Also check for missing pictures. If you need to select a colour click the dropper tool, click on the colour you want and bucket fill the missing area.
To zoom into your image click the magnifying glass icon and click on your image. A missing pixel looks like a grey dot on your image. To fill it in click the pencil tool, select your brush and your colour. Go over the pixel with the pencil until it is no longer visible. Do this to all missing pixels.
If your picture still has a grey checkerboard area underneath it add a new page, select a white background and click ok. Select the bucket tool and fill the area with the colour you want to be at the bottom. Drag the layer from the top and place it underneath your drawing layer.
If you want to cut something out of your image, choose the crop tool and drag it over the area you want to keep. Click on the image to cut it.
To save your image select file, export as, choose where you want to export the image to and save as a png or jpg. Click export. If you are exporting it as a jpg, set your quality to 100.
If you want to save the image so that you can work on it again go to file, save as, rename the file as you want and save as an xcf file.
You can close the Gimp program. Now you have an image that you can use in your books.
Gimp and Inkscape are free to download.
It might take you a while to get a hang of things, but soon you’ll be able to digitize your images with ease.