Brightness and contrast now read in percent

You open a dark image and the boundary you need to trace disappears into the background. View → Brightness Contrast brings the edges back, but until now the dialog reported each slider as a bare factor such as 1.50, a number you had to translate before you could note it down or tell a colleague what to set.

The dialog now reads in percent. 100% is the image as it loaded, 150% is half again as bright, and each slider runs from 0% to 300%. The number tells you where you are before you touch anything.

Nothing else about the dialog moved: same range, same neutral position, and the same picture on the canvas. The v7.3.0 implementation drives both sliders through one lookup table and leaves every slider combination rendering exactly as it did before, transparent PNG regions included.

The adjustment is for your eyes only#

Brightness and contrast change what the canvas draws, not what Labelme stores. The annotation keeps the original image data, so you can push a dark frame to 200% to place a boundary and the dataset you export is untouched.

Each image keeps its own values, so returning to it restores the same view. Turn on Keep Previous Brightness/Contrast in the View menu and the next image opens with the setting you just used, which is what you want when a whole folder was shot under the same bad light.

The change ships in Labelme v7.3.0.