Colour Plots Using: Plotterfun and a Pen Plotter

There is a nice application on the Web called Plotterfun.

I cannot take any credit for the code; it has been revamped/ported from previous versions with more added by: Mitxela

Details and source can be found here on GitHub: mitxela/plotterfun

This instruction is the process I take to make Colour Images using Plotterfun.

There are many Algorithms to choose from.
I will be using Linedraw for this example.

Note!

Photos of the results may not show the true result.

There is a thing called Image Interpopulation on cameras.
Cameras try to do magic, they make the Images larger and fill in gaps, the camera on my phone does not give me an option to save RAW Images. So, Photos may look fuzzy, the screenshots when making a preview may give a better representation.
Saying this, our eyes (brain) will do the same thing when looking at these types of images.
So, when you have seen the original photo they may look better, ha-ha.

Supplies

Obviously, you need a plotter and computer connected to the web.

We are drawing images using a Plotter. With a pen, a pen only draws lines.

Graphics Software will also be needed to prepare the images for conversion.

Both Bitmap and Vector graphic software will be needed.
I will be using CorelDraw and Phot-Paint.
Any software that can handle the type of graphics can be used. Inkscape is free.

I have found thick matt paper gives the best results.

This is using ball point pens.
My plots will be for A4. (Larger depends on how fast you want to do the images).

Pens: four colours will be used. I will be using the CMYK color model.

Cyan (Light Blue)
Magenta (Red/Pink)
Yellow
Key (Black)

If you want to make a tool for your plotter to hold more than one colour pen, see my 10 Colour Plotter Pen

This process can be done changing pens manually.

Step 1: Prepare the Image

The Image I am using is:

Height = 1000 pixels.
Width = 1200 pixels.
It starts of as a 24-bit RGB.

This size is a good size to view results on the computer screen.

The size is not too much of an issue at the start, as we will be adjusting things by eye (looks).
The ratio of height to width should be as you are going to print.
When it comes to plotting the converted SVG version I will be scaling to fit my paper.

Because we are going to make a colour plot, we need to split the image into the colours we are going to use.

We are going to use four pens.

Cyan (Light Blue)
Magenta (Red/Pink)
Yellow
Key (Black)

First, we need to convert the image to a CMYK type image.

This is so we can separate and make different versions of the image.
If we look at the image channels, we can see the separate four colours.

Next, we need to save these Chanels into separate files.

Turn the Channels into separate images.
Save each created image into a folder.

The created files will all be Grey-Scale images.

Each Grey-Scale image will represent the amount of the colour it is representing in the original CMYK photo.

We now have all the Bitmap Images we need for conversion.

Step 2: Plotterfun Settings

I am doing this using the "Linedraw" Algorithm, Not many settings with this one.

Set the Algorithm to "Linedraw"

Load you original colour image and click "Use image" button.

As I have mentioned Size is not an issue at the moment.
Obviously if it is too big then it will take longer.

There are 3 sliders, have all check-boxes ticked:

Contour detail: The higher the value the longer the line. Slid to your preference.
Hatch scale: The higher the value the less lines there are. Slid to your preference.
Noise scale: This makes the lines wavy. I just leave this at value 1.

Points of Note!

The image does not want to be too crowded. Using the Colour Image we want it to look fairly sparse but give a good overall representation.
When we use the CMYK Images, the lines will multiply 10 to 100 fold.
Light colours don't want to be present at this stage.
Only the shadowing of light areas should be present.

Hopefully the Image shown will give you an idea what you want.

Once you are happy with your settings, we keep these settings for creating the SVG images using the CMYK Images.

Step 3: CMYK Images

We repeat Step 2 with each of the four CMYK Images without changing the settings.

But when each one is converted:

We click the "Download SVG" Button.
It will be given an Auto Name, but we want to save them with the same name that the CMYK Image was named.
It will be saved as an .SVG Image.

We should now have four .SVG images in our folder named:

Cyan.svg
Magenta.svg
Yellow.svg
Black.svg

This time there should have been more lines.

Some may look a mess, but remember it is the lighter colours that have the most lines.
Even though we have a black, a CMYK Image still makes dark colours using CMY.

Step 4: Adjustment and Preview

Now we have the four .SVG Images made, we can now modify and preview what the output may look like.

For this we use Vector Graphic Software.
Oh, by the way, SVG stands for: Scalable Vector Graphics.

I will be using CorelDraw.

I will do the process for one Image (Black).
All SVG Images need to go through the Same process.

As I have mentioned, the "S" in SVG stands for Scalable, so the first thing to do is scale each SVG Image to a size that will fit the paper it is going to be Plotted on.

Every thing you do to one SVG Image you must do exactly the same to the other SVG Images.
Except for colour, I will be making the colour match whatever the SVG Image represents.

Size

Make sure the canvas/work sheet in the software is a size that will fit your plotter paper/work area.

The canvas/work sheet in the software must be equal or larger than the image.
Setting the size of the canvas/work sheet, sets the origin and boundaries when the image is converted back to an SVG file.

My Plotter will do: 260mm x 280mm. So, I am going to make my work area 200mm x 200mm.

You will see in the image above that after setting the canvas to 200mm x 200mm, the image is too big to fit.

I will now scale all images to fit the canvas.
The Images will not be the same size.
Find the largest (In my case it will be the widest)
Use a Percentage to resize the image, this way all images will be reduced by the same amount.
I made the width fit, with the ratio locked the height fit easaly.
Make sure you don't move any image.
At the moment all is scaled around the centre.

SVG

SVG files are actually DOM files (Document Object Model).

If you know how SVG files work and know the key words used.
You can actually open them up in a text editor and edit them.
In an SVG Image, items (Lines, Circles, Curves and the like) can be grouped or merged together as one item.
Currently the SVG Files that we created have all the items merged as one.
For my software to convert things to G-Code I need items separated (brake apart). (They can be grouped)

Before I un-merge (brake apart) each image, I am going to rename it to the colour it represents.

This is because in CorelDraw when I brake apart an Item, all the Items it brakes the Item into have the same name.
This will help Identify things when making the preview.

Break all Images into there separate components.

Once the Item has been broken into separate Items, group them together.
Grouping Items is not the same as joining Items together.
It's like putting things in a folder.
Re-name the group with the name of the colour it represents.

Select the Group and change the properties of the Items.

This is just for the Preview, these changes wont effect the outcome.
I find a pen width of 3px gives a good representation.
Change colour mode to CMYK then each image will have only its own slider set full. (Others set to Zero)

In the folder where you have these images, create a copy of the black and re-name it "All"

Open this file in the image software.
In the Image software copy the Groups: Cyan, Magenta and Yellow to the new file which should already contain Black.
The file named "All" is just for preview, to give you an idea what it will look like.
It is good to know if it is going to look good, each colour can take a couple of hours to plot.

Rearranging the groups will give a different look.

I found Black, Magenta, Cyan, Yellow gave the best representation.
In the preview, colours under others are hidden.
When plotted Colours are merged.

Step 5: Saving CMYK Images

Because I am using CorelDraw to edit the images:

CorelDraw's own file type is .cdr
The CMYK files need to be saved as SVG.

I use CorelDraw's Export File function to save the CMYK files in the SVG format.

Points of Note About SVG!

Not all software save SVG Files the same way.

SVG Files are quite simple to create.
But there are many ways to create the same shape.
So, to convert SVG to some other format is a different matter.

This is why I have tried to brake it all down to one/single level of items inside the SVG Files.

I overwrite the original SVG Files.
My Software will not convert the original files made by "Plotterfun"
If you are using other software try not to have rotations or transposes of items.
The software I use to convert to G-Code, is what I have written, It's fairly basic in what it can handle.

Step 6: Convert to G-Code

It's My software that I use to convert SVG Files to G-Code.

There may be other software about or online applications.
My software can be found here: Tim's XY Plotter: Tim's XY Stepper Controller (tims-xy-plotter.blogspot.com)

The conversion Application is a Sub-Application of my main Plotter Controller.

There is a button called "Create G-Code" This will start the application.
I have made it to do all sorts of conversion.

Click the SVG Tab.
Select the SVG File to be converted.
I don't know what settings your plotter will require, you may have to edit the G-Code regarding Pen up/down.
When ready click the Convert button. This may take some time depending on how large your plot is, or how dense you have made it. My example 200x200mm Yellow was about 1 minute. The application may look to freeze, give it time.
Save the G-Code. The text in the blue boxes can be edited before saving if you wish.

Step 7: Plot

Plot each file with it's relevant coloured pen.

Because it is a plot with pens, any type of pen can be used.
Could be felt tip. Gel pens with glitter, even fountain pens.

This took me about 8 hours to plot all colours.

If you have a professional plotter it may take a lot less time.
My plotter is self made and I haven't given it a memory buffer yet, all commands are sent one at a time.

You can of course just print the Preview on a Colour Printer.