en:traffic:documentation:stltasttransparency

Keyboard Shortcuts for Picture Transparency:

General remarks about transparency:

Pictures that are resident in .EXE, .DLL and .SCR files are never transparent. This attribute can therefore not be altered by Traffic.

.GIF files contain information about their structure including whether or not the file is transparent and which colour indicates the transparency. Traffic cannot change the transparency index of a .GIF file. That must be done in a graphic editing program.

BMP and .DIB pictures are by their nature not transparent. However, Traffic can use these pictures and render them transparent in that it sets the transparency of the picture from the upper leftmost pixel in the picture. The command CTRL+T switches the “transparency” of BMP or DIB files.

Pictures contained in the TVL files are similar to GIFs in that their transparency is saved as part of their file structure. Because the TVL file type is unique to Traffic, it is currently not understood by any commercial graphic program. With the CTRL+T command, one can toggle the transparency of the picture. When the transparency is toggled on, the transparent colour is usually taken from the upper rightmost pixel in the picture; however, it is possible to alter which pixel Traffic uses to determine transparency.

Ct	Changes the transparency of all of the selected files in the TVL library. Customarily the transparency is taken from the upper rightmost pixel in the picture. If the transparency has been turned on by previous use of this keystroke, repeating the keystroke toggles the transparency off.
C1	Sets the transparency from the upper rightmost pixel of the picture. This is the standard setting.
C2	Sets the transparency from the bottom leftmost pixel of the picture.
C3	Sets the transparency from the bottom rightmost pixel of the picture.
C4	Sets the transparency from the bottom midpoint of the picture.
C5	Sets the transparency from the most common colour in the bottom region of the picture.