You do not need calipers to measure things like that, but can easily do it from a picture.
A simple method is to just use a screen ruler program, and then use something of a known size to calibrate your scale.
For example, from the IC on the right you have 6 pin pitches in about 138 pixels, so each pixel is: 6*2.54/195 = 0.07815 mm
The SMT resistors are about 13 by 22 pixels, and that makes them about 1.0 by 1.719mm
These measurements are somewhat between 0603 and 0805.
With a higher resolution (and well framed, taken perpendicular, etc)photograph, measurements can easily be made much more accurate.
The simplest way to do this is load it in any pixel program and start counting pixels, but using a screen ruler is already a bit better. FreeCAD has the possibility to use a photograph as a background image, and then scale it precisely to some known size (for example the IC) and after that a sketch with accurate measurements can be laid over that.
There is also commercial software for this, but I have not used it.
Having good pictures is important for accurate measurements.