: How to vectorize a graph from a raster image I have an image of a graph and want to redraw this graph in Illustrator. Full size image Is there any "trick" to do this? I am trying with

@Rambettina927

WebPlotDigitizer is a great tool to extract raw data from a graph when you only have an image. I often used it in academic work when I only had an old pdf, or even just a book.

I tried it with your image using a two pixel window and an approximate linear scale between 0 and 10 for X and Y axis and here is what I get :

1.0485631998258123;0.7095385171292392
1.0951846161987482;0.6818787962214152
1.1419973891314237;0.6237933823149842
1.1977691282700924;0.6182614381334197
1.2438164749638092;0.6818787962214152
1.2773560610709063;0.7648579589448872
1.2985096589475817;0.8478371216683591
1.3167233242246206;0.9059225355747884
1.3349891776543155;0.9557100332088719
1.353202842931354;1.0137954471153012
1.3899433024013694;1.080178777294078
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1.4627979635095243;1.3125204329197988
1.480855064328594;1.3954995956432708
1.5268328268187692;1.4701808420943951
1.5829002988224903;1.4176273723695303
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1.6469699542335063;1.5697558373625622
1.6559985046430412;1.6112454187242964
1.6648704905946072;1.677628748903075
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1.7280181553086957;1.9763537347075726
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1.799933429669038;2.358057883235542
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1.8533740979890598;2.7231661992188165
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1.871639951418755;2.7729536968529
1.880511937370321;2.839337027031677
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1.916860985695414;2.9679547292530586
1.9350485568961246;3.0301891012956617
1.9532622221731635;3.0882745152020927
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8.509885989042056;1.8906085998933193
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10.269948833425698;2.676144673675516
10.316439779416992;2.669229743448561
10.354093531558492;2.590399538861263
10.373090019125375;2.524016208682484
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10.410978617953827;2.407845380869624
10.429922917368055;2.3497599669631946
10.448867216782281;2.2916745530567653
10.467811516196507;2.233589139150334
10.48678190968706;2.171354767107731
10.4964628120048;2.1091203950651263


And then you can use any other software able to plot the path corresponding to these coordinates.

For example, I used python and matplotlib to generate this pdf.
The script used to read the data from a file and create a pdf is below:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure(facecolor='w')
ax = fig.add_subplot(111)

X = np.loadtxt("data.txt", delimiter=';').T
ax.plot(X[0], X[1])

plt.savefig('image.pdf', bbox_inches='tight')


Actually, you can also export the result in svg format with 'image.svg' in the last line.
You can then load the pdf (or svg) to illustrator (or inkscape in my case) and scale the curve to fit the original :

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@Margaret771

No problem because your image is quite clear. At first make a version that has only the curve. This is the place where some brainwork relly pays off if the curve is complex or the underlying coordinates are dense. See the image:



Make two copies of the curve layer, select the top layer, goto Image > Adjustments > Hue/Saturation and change the blue to red. You can also shuffle the color channels, but that needs a good underhood knowledge, so adjust the hue.

Give to the hue shifted channel blending mode = Divide. That knocks the coordinate graticule to white, but the curve survives, altough gets some color variations due the unsharpness of the image.



Merge the two upper layers. Turn the blue and cyan to black. Again goto Hue/Saturation and adjust the brightness of cyan-blue range to extreme minus. Note the range selection sliders:



Copy few coordinate lines at different places of your original image to the cleaned layer for easy realignment. Paste them in place!

Copy the clean layer to the clipboard and paste it to Illustrator. Do a live trace. See the settings. Nearly all is essential:



I have used this software actively, but I'm still so clumsy of my hands that nothing beats a good automatic tracing. Unfortunately good automatic tracing is often impossible. Your image is in the premiun class of the traceables.

Here only the strokes are traced, not the fills. The selected accuracy is high. The treshold also is high to get the coordinate line snippets captured.

Copy and paste from Photoshop your original image. Send it to back and align with the trace to see the possible faults. At least there's a small gap near the right end and a stray dot. The gap is not in the following screenshot.



Expand the trace and ungroup it to be able to make edits. Obviously you want to remove the extra coordinate lines, draw some new coordinates, fill the gap, change the color, add texts etc....

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@Shelley591

If you have data, this is very easy, just select the graph, copy it, then paste into a .ai file and it will be converted to vectors automatically.

If you have an image, it will be a bit more complex (well, a couple additional steps) and you'll need PS as well.

Assuming this is the case, open your image in Photoshop, then adjust curves until the grid lines disappear.

After this, you have 2 options:


Option 1 (easier on Illustrator): Go to Filter --> Stylize --> Find Edges. Apply. This will give you an slightly wider line.
Option 2: With Magic Eraser Tool, delete all the white. Once done, select your layer, then Blending Options --> Stroke and use Size:1; Position: Center


Now open the image in Illustrator. Click on the graph to select it and go to Image Trace on the top of your screen. If you used Option 1, simply choose the 3 colors option and it will render an exact line.

If you chose Option 2, select Technical Drawing (or play with custom values). In this case, you'll get a very close approximation, although not exactly the same, but you can adjust it (or if the small differences don't matter, simple leave it as is!)

By doing this, I got this result (gray line is my version, overlapping yours)

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@Berumen635

To get the blue line I would use Image Trace with setting High Fidelity Photo. After Tracing expand and upgroup the object.

The blue line may have survived the tracing intact and clean. In that case just select and use it.

If not, use the magic wand tool to select everything that is the blue line, lock results and delete the rest, unlock blue line, group and use.

After tracing and expanding you can just start deleting stuff that is not the blue line until it is the only thing left.

Alternately, without tracing, you can carefully trace the blue line manually with the pen tool. This will give you a very crisp vector path that you can control shape and color.

Once you have the blue line separated you need to recreate the grid. (I don't think those thin grey grid lines will survive the tracing, test and find out)

To make that grid I would make a rectangle the same size, no fill and thin grey stroke. Then with the rectangle selected go Object>Path>Split Into Grid. Specify the rows and columns in your graph and hit okay.

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@Murray976

It's faster, in my experience, to grab the Pen Tool and trace, the graph manually. I've dealt with this issue for nearly 20 years. Nothing beats manual tracing unless you have the actual data amounts and can plot the data again.

Any method to trace or otherwise grab the data line from a raster image, generally takes far more time and effort than just manually tracing it.



Under 1 minute

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