![]() ![]() (How do I know? I am an actual practitioner.) Perhaps you should avoid doing an "internal" one for the time being, as it requires a re-draw of the ruler and a re-labelling on the scale marking as and when the user scrolls the picture in the viewport (when the picture is bigger than the viewport). ![]() In general, "external" one is much easier to do. Againt the ruler(s) you can measure other items you have on desktop, A ruler can also be drawn for "internal" use, similar to the one you see in PhotoShop - against it the current image is to be measured. when you invoke the "ruler" program, it stays always on top of the desktop and is moveable by user's dragging on it (user can also right click on it to switch scale units, and to set to vertical only, horizontal only or both). Please also note, a ruler can be drawn for "external" use, e.g. As the value increases, inaccuracy is getting more serious. (2) The scales for both CM and Inch are incorrect - they fail to take into consideration of the existence of fractionss which need to be adjusted on conversion between Pixels and CM, and between Pixels and Inches. ![]() Its value labels are at a 50-pixel interval, thus when you see 2, it means 100 pixels, 4 means 200 pixels, and so on. (1) The one at top (black one) is drawn correctly scalewise, but the numerical labels are not quite. Whilst the code does give you a general direction on how to draw a ruler, you should note the following if you go down into the detail: ![]()
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