Using Neural Networks to extract multiple parameters from images
A CNN could be a good choice for this task if you expect variation in the original image scale, rotation lighting etc, and also have a lot of training data.

The usual CNN architecture is to have convolutional layers close to the input, and fully-connected layers in the output. Those fully-connected layers can have the output arranged for different classification or regression tasks as you see fit. Predicting the values of parameters describing the image is a regression task.

If you want accurate measures of size, you may need to avoid using max pooling layers. Unfortunately, not using pooling will make your network larger and harder to train - you might get away with strided convolution instead if that is a problem for you.

If your input images are very simple and clear (because they are always computer generated), then other approaches may be more reliable. You may be able to reverse-engineer image production and derive simple rules such as identifying lines, corners, circles and other easy-to-filter image components, and make direct measurements. There may also be a middle ground in complexity where extracting this data as features and using it to train a simple NN (or other ML model) will have good performance.