How to remove the background from an ink drawing?
I prefer drawing on paper, especially with ink . The organic texture, the modulating lines and occasional speck of ink is deeply satisfying. When it comes to colouring a drawing watercolour on water-proof India ink is a viable option. However, in this post I’ll explore how you can extract your inked-in lines and get them ready to receive dollops of digital ink. This post solves the key first step in a workflow which involves analog inking followed by digital colouring. – which is, to extract the ink-lines from the scanned image ( separate it from the background ).
I’ll use this drawing of mine, called “The Golden Frog” as a working example.
What’s provided below is a step-by-step process to achieve this result on Affinity Photo – but the principles can be applied to any graphic design software like Adobe Photoshop. Do note there is a lazy, inefficient way of achieving this result – by setting the linework layer’s blend mode to multiply – however this quick fix will lead to problems with colors, transparency and contrast further down in the work flow. The other alternative is to manually erase the background – which is regressive and time consuming, which is probably why you are reading this post.
The efficient method:
1. Scan the image in a decent resolution in Black and white. I explore what is the right resolution in an upcoming post ( for now, work with a scanner resolution of 1200 dpi in black and white)
2. Open the image in Affinity photo
3. Black and white image – Use a gradient map to ensure that the black lines are as black as possible and the white background is really white. Further, use a “burn” tool to ensure that all grays are turned to black. In affinity photo: Layer >new adjustment layer > gradient map.
4. Invert the image – Select the line drawing (by default called “background”) and layer> invert
5. Select the background and rasterise to mask. It may seem to have disappear for, but it is still there. Add a black fill box, across the entire drawing, at the bottom of the layer stack – to bring back the lines
6. Select all layers – and right click – merge visible. Retain the new pixel layer and delete every thing else
7. At this stage, you can use the erase tool to clean up any unwanted specks and use the brush tool to fill in any missing lines
And there you have it – you have successfully arrived at a pixel layer with only your linework, with full freedom to manipulate it’s color and texture. In my next post i’ll explore the method to block-in colors in the empty spaces and vectorise those color blocks for full design control.
Here is the completed digital painting:
