I need a program to measure angles from picture

[DiTBho]

So, I am analyzing a lot of bicycle frames, all classic (70s, 80s, 90s), and during my studies I am trying to understand their geometries in terms of biomechanics.

I need to extranct geometry parameters from frames.

Unfortunately I cannot work with real frames, just pictures, on which I'd like to make measures (at least):
- tubes length
- angle between two tubes

Is there a program I can use to load a pic as background layer and make measures over it?

Opensource, if possible, so I will run it on my risc workstation.
Thanks 

[DiTBho]

(I'm secretly looking at the Marvin' and Greg Lemond's frames.
I drove a US-made Marvin 3AL-2.5V-TI in the 1990s
and took many photos to capture all the geometry secrets of it)

[BeBuLamar]

Some kind of CAD program can do that. You generally import the picture into your drawing then draw lines along the tubes. The program can tell you the angle between those lines.

[SiliconWizard]

Or you can do it the old way, print the pictures and use manual tools.

[NiHaoMike]

GIMP can do that.

[sokoloff]

I’d import them to canvas in Fusion 360, then draw sketches over top, then inspect the sketch lines using the measuring tools.

[golden_labels]

(assuming that “RISC” stands for “RISC-V”)

I suspect any major graphics or CAD package will be hard to compile for exotic platforms, because of their sheer size and dependence on platform-specific rendering handling.

GIMP measure tool offers that option, but no idea if GIMP can run on RISC-V.

While that may sound like a joke and initially I perceived it as such… depending on how good precision you expect and how many frames you need to measure, a transparent protractor may actually work. Those are dirty cheap, available as school supplies, mostly platform independent.⁽¹⁾ Just remember about the parallax error and make sure your pixels are square.

⁽¹⁾ Non-flat CRT screens are unsupported. Some non-LCD flat displays may cause issues.

[Ed.Kloonk]

GIMP measure tool offers that option, but no idea if GIMP can run on RISC-V.

I'll bite. Why wouldn't it?

[radar_macgyver]

You can use WebPlotDigitizer, it has an angle measurement tool.

[SiliconWizard]

GIMP measure tool offers that option, but no idea if GIMP can run on RISC-V.

I'll bite. Why wouldn't it?

While Linux runs on RISC-V, I have personally no clue if you can use a desktop on those yet. If that is the case, then there shouldn't be any problem compiling and running GIMP indeed.
And knowing the OP, I'm pretty sure it is not RISC-V anyway, but some older RISC platform.

[DiTBho]

Risc = { hppa2, ppc32, ppc64, mips32, mips64, mips5+(r18200), riscv, arm, arm64  }
Planned stage4-2022-11 = { hppa2, ppc32 }

Sorry no time at the moment.

New plans, 2023-04, 2023-06, ... Maybe

[DiTBho]

Use a desktop on those yet. If that is the case, then there shouldn't be any problem compiling and running GIMP indeed.
And knowing the OP, I'm pretty sure it is not RISC-V anyway, but some older RISC platform.

Haiku can already boot and run a full (but slow, pure framebuffer) desktop on Radeon pcie + riscv mobo.
You need a special mobo with pcie
Only a few pcie video cards work (pci 32 bit transactions only)
Smp doesn t work.
7 minutes from boot to desktop (and it s not x11, it should be faster)

Linux .... Well has better kernel and kernel modules support. But it s in the same "experimental" basket.

[DiTBho]

GIMP can do that.

Ok, I can compile GIMP, can you tell me more about the trick?
Are there "meters" to measure angles and length? Plug-ins or already supported functions?

[Ed.Kloonk]

You just select the measure tool in gimp and enable the tool window, then using shift and the mouse button draw the angle you want.

[jonpaul]

Autocad or Photoshop.

Search : FIND ANGLE

j

[SiliconWizard]

You could alternatively use Inkscape - I think it has measurement tools, although I'm not very familiar with them.
So you'd import your pictures in Inkscape, have them vectorized, and then measure. The benefit is that you'd work with vector graphics which would make things easier. The only thing is that I don't know the measurement tools much. There seems to be some info on the forums: https://inkscape.org/forums/questions/measurement-m-tool-angle-reference/

[Nominal Animal]

I have used Inkscape for this, but in a different manner to what SiliconWizard described.

You see, you must transform the image so that the measured item in the image is in the same plane as the image, i.e. perpendicular to the screen, with correct scaling on both axes.   I import the image, and use Object > Transform until it is in a suitable orientation.  I then add a new layer, and often use the Bézier curve tool to draw lines.  I also use the File > Document Properties to set the page size so that I can easily measure things in millimeters in the image.  (If you draw a line whose length you know, you can divide the document size by the relative error in the line length, to get the scaling exactly correct.)

The Measurement tool measures distances between two points, and the angle that line makes with the horizontal axis.  You drag a "line" from the apex of the circle, to the non-horizontal end point of the arc.

When I want some arbitrary angle, I use the Circle tool. (If you press Shift+Control, you'll drag a "line" from the center of the circle to its perimeter.)
First, make sure View > Show/Hide > Tool Controls Bar is ticked.  Then, draw a circle, either by pulling a diagonal of its axis-aligned bounding box, or by pressing Shift+Control and pulling a radius.  You'll see the Tool Controls just below the menu bar.  Make sure Rx and Ry are the same, so that you'll get a circular arc, not an elliptical one.  Set Start: to 0, and End: to for example 45.  Select the Select tool (simplest is to press ESC or F1), and click on it.  The scaling arrows around it change into rotation arrows.  Move the + in the center to the apex of the wedge; it is the rotation center.

You will want to use the Select tool and the rotation handles to adjust the initially upper edge of the wedge, and the arc end angle for the lower edge of the wedge.  (Again, selecting the object, and then clicking on it with the Select tool, switches between rotation and scaling handles.  Double-click to change to Tool Controls.)

The idea is to keep Start at zero, and only change the End angle, so that the End angle directly tells you the angle.  It is clunky at first, but you quickly get used to it: just use the object rotation to set the counterclockwise edge, and the circle arc tools to set the clockwise edge of the arc.  Whenever you have the Tool controls visible, you also see the radius of the arc; just keep Rx and Ry the same.

If you just use the arc control points –– which is easier and may be faster ––, you'll have to calculate the arc angle yourself, by substracting Start from End.  They are always in degrees.

When you also have View > Show/Hide > Snap Controls Bar checked/visible, the "Snap an item's rotation center" (fifth up from bottom) is very useful, when you move the + in the center to the apex of the wedge, as it snaps precisely there then.