The Display UL Coordinates alternative can be chosen instead, to have the origin at the upper-left corner and with the second coordinate increasing downwards. If this is done, images in the TEX document using such coordinates should be preceded by the \MacintoshOrigin command.
To mark a point within the image, simply click with the mouse at the desired point. A small window will pop up, as in the screen-shot below, allowing a label to be typed and the selection confirmed.
After the first point has been chosen a Log-window appears, containing bounding-box and other information, as well as data for the first marked point. A line of data is added for each subsequent point. Within the image the point is marked by a numbered cross. Guide-rules help position the cursor accurately: gradations may be inches, centimeters, or pixels. The Log-window can be seen in the above picture. Since it contains just plain text, the Log can be edited at any time.
When finished with an image, click its close-box (in the upper-left corner); this also adds the closing comment to the Log. Finally close the Log-window and Save As..., choosing whatever name is desired--usually ending .bb, though this is not compulsory.
\MacintoshOrigin | allow for coordinates with origin at upper-left |
\EndLineAdjust | adjust for awkward line-end characters |