I would like to scale a raster image inside Illustrator to a precise dimension - for example, a mechanical drawing with dimensions. I can draw a precise length line over the dimension, but can I then scale the line and the image precisely to the desired length.
I realize I can do the math and use a scale percent, but I was wondering if there's a faster way.
Using a calculator to find the right scaling is a good idea, drawing tricks do not help substantially. There's no such one click transformation which sets a wanted part of the drawing to wanted size.
But the calculator is not needed if you can reliably multiply with small integers in your head. The next trick applies it. Have smart guides and snap to point ON (+no other snaps ON) to be able to do it.
A shape, the black arrow should be 40 millimeters long in the drawing, but it's shorter.
Make a copy of the arrow (blue) and rotate it with the rotate tool horizontal.
Place copies of the blue arrow consequently until you have a chain of them which is wider than the original image+arrow. Here only 2 was needed.
Select all. Set the width in the infobar to 80 mm, be sure the proportionality lock is ON before changing the width.
If you're lucky no multiplication is needed. For ex. in this example rotating the blue arrow vertical and setting the height to 40 mm would have been enough.
It is possible to do this in illustrator without cranking up the calculator (it is also slightly more accurate as typed numbers only come with 5 digits of precission). 2 ways in fact.
Method one. Draw a line that represents your measurement. Copy the line and scale the original it to the size you wish the line to be. Make sure the measurement line is below the line you use as current scale and that they share one endpoint. Select your image and original measurement line. Switch to scale tool (no dont use the selection tool), click on the common end of measurement lines this puts the scale pivot to that point there. Then holding shift, drag the endpoint of your original measurement line. Done.
Thigs to watch out for this method does not work if your line is near horizontal or vertical as that would trigger nonuniform scale. So rotate your image first.
there is another variation of this theme but i will not describe it.
You can also use illustrator as a calculator. Every illustrator input does allow you to type in math functions as long as there is just one function. You can allwsy tab out to add more calcualation.
