Number Knitting #2: Colorizing Photos in Photoshop

In my efforts to republish the Number Knitting book, I am trying to recruit knitters to help me reknit all the patterns from the book, so that I can take new photographs. In order to breathe a bit of life back into the photographs, I am colorizing them in Photoshop.

Here is the photo as I originally scanned in it. It has low contrast and looks pretty boring.

Checkerboard Design Table Mat

I've been experimenting with a few different ways to colorize my images, and here's what I'm doing now. I'll likely change it up, as I get more sophisticated with colorizing. But I find this method to be pretty flexible for what I need.

1. So in Photoshop, I started by adjusting the curves. I just clicked Auto.

Auto Curves

2. I set the blend mode to multiply.

Set Blend Mode to Multiply

3. Then I created a new layer, moved it below the image, named it,  and went to Layer > Layer Mask > Hide All. The first and most important thing to understand when working with masking is that black hides and white reveals. So I start by hiding everything, and then I'll paint in with white to reveal just the parts that I want to be blue.

4. Make sure that you have your pixels portion of your layer selected. See the little border around the transparent pixels in the image below?

5. Then go to Edit > Fill > Color > and choose a nice blue.

And the result is nothing so far. But now we'll start painting in the areas that we want to be blue. 

6. Select your paintbrush tool, and choose white for your foreground color. Start painting in around the parts that you want to be blue. Then fill in the area clean up the edges, adjusting your brush size and feather as needed. You can adjust your brush size using the [ and ] keys.

• ] will increase the size of you brush.
• [ will decrease the size of your brush.

You can also adjust the feather of your brush using the keyboard.

• Shift + ] increases the hardness (decreasing the feather).
• Shift + [ decreases the hardness (increasing the feather).

7. It looks pretty good, right? 

If you go to the Channels panel, and turn on the mask, you can see that there are still some areas that I missed. See the light red poking through the blue near the edges of the table mat?

Now I can more easily see those areas and fill them in.

8. Use this same technique to paint in all the Blue areas.

9. Then repeat this process for the light blue squares.

What I really like about this technique is that now, changing the colors is as easy as adding a different fill color.

You can even add a gradient fill, to mimic variegated yarns.

10. Now that I have the picture colored the way I want, I can choose some yarns to match it; Because the objective of this project is not just to colorize old photos, but to get people to knit these projects. The colors in Photoshop need to be a representation of the actual materials they'll be using the knit the pattern.

The original pattern calls for cotton yarn in an afghan weight. In modern day terms, that means a worsted weight yarn. Just this morning, I discovered some great worsted weight cotton yarn, in a variety of colors, at an affordable price. Conveniently, enough, it's called "Dishie" (because it is super durable and suitable for dishcloths and other kitchen-related tasks).  Cotton yarns are typically rather muted in color.

For my original colorway of blues, I'll choose Dishie in Blue and Azure.

But if you look at the original blue colored photo, the blues I chose are too intense.

By reducing the opacity of the blue layers, I can more closely match the color of the yarn that I'm specifying for the checkerboard table mat pattern. I reduced the Blue layer to 80% and the Light Blue layer to 60%.

Here is the final table mat, knitted in Dishie yarn.

Checkerboard Design Table Mat