# How to make a standalone colorbar

**URL:** <https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164>\
**Category:** Q&A\
**Created:** [August 8, 2023, 3:01pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164 "2023-08-08T15:01:21Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![pa345](https://avatars.discourse-cdn.com/v4/letter/p/e79b87/32.png) [@pa345](https://forum.generic-mapping-tools.org/u/pa345)\
**Post date:** [August 8, 2023, 3:01pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/1 "2023-08-08T15:01:21Z")

</div>

I need to make several figures and then splice them together at the end. I am trying to make a colorbar by itself to add to the final figure. Here is my attempt:

```
gmt begin fig png 
  gmt makecpt -D -Cjet -T-1.5/1.5 > t.cpt
  gmt colorbar -Rd -Ct.cpt -DJBC+w6i/0.5c -Bx0.75 -By+l"nT/kA" -Y0.1c
gmt end

```

However, I get this error:

`psconvert [ERROR]: Unable to decode BoundingBox file /home/user/.gmt/sessions/gmt_session.26811/psconvert_27348c.bb (maybe no non-white features were plotted?)`

If I use the above commands with plotting maps, it works ok, but not by itself. Any ideas?

---

<div class="post-metadata">

**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\
**Post date:** [August 8, 2023, 3:04pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/2 "2023-08-08T15:04:55Z")

</div>

Do you mean [-H](https://docs.generic-mapping-tools.org/dev/makecpt.html#h)?

---

<div class="post-metadata">

**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\
**Post date:** [August 8, 2023, 3:16pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/3 "2023-08-08T15:16:59Z")

</div>

Or get rid of that \> t.cpt (which would require -H, but why try to mix classic and modern mode?) and also the mention of t.cpt elsewhere.

---

<div class="post-metadata">

**Author:** ![pa345](https://avatars.discourse-cdn.com/v4/letter/p/e79b87/32.png) [@pa345](https://forum.generic-mapping-tools.org/u/pa345)\
**Post date:** [August 8, 2023, 3:19pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/4 "2023-08-08T15:19:40Z")

</div>

Ok I removed the \> t.cpt and -Ct.cpt, but I get the same error as before

---

<div class="post-metadata">

**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\
**Post date:** [August 8, 2023, 3:42pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/5 "2023-08-08T15:42:07Z")

</div>

Says you have not plotted anything

---

<div class="post-metadata">

**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\
**Post date:** [August 8, 2023, 4:51pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/6 "2023-08-08T16:51:18Z")

</div>

This works for me.

```
  gmt makecpt -D -Cjet -T-1.5/1.5 > t.cpt
  gmt colorbar -Ct.cpt -Dx0/0+w6i/0.5c -Bx0.75 -By+l"nT/kA" -Y0.1c -png fig

```

 ![fig](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/2X/5/5caa8b875090d2ed4bcf57d5a696a4d5319af9b1.png)

---

<div class="post-metadata">

**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\
**Post date:** [August 8, 2023, 5:25pm UTC](https://forum.generic-mapping-tools.org/t/how-to-make-a-standalone-colorbar/4164/7 "2023-08-08T17:25:51Z")

</div>

If you use -DJBC then how will GMT know where that is without a -R and -J? Also, **colorbar** does not take -R.