Fonts ok, adding alpha transparency

A project log for HOMER

2D GPU: HD resolution @ 60Hz, HDMI, double buff, hardware acceleration, USB config upgrade, ... For ARDUINO & other ┬ÁC

monnolivmonnoliv 10/18/2015 at 18:490 Comments

Converting and adding (mono) true type fonts is done. Text is displayed in 16 grey-scale values. Displaying text on black background is beautiful but displaying the same text on another background colour or over an image is ugly. I decided to work on alpha transparency.

Alpha transparency

If one wants to display text with a specified colour on an image or other background, the system must do a calculation between the pixel text weight colour (16 values) and the background pixel colour (240 colour values, BTW I've fixed the palette colour content to 685-RGB values + 16 grey-scale). This calculation has to take into account a user transparency selection (also 16 values). I've implemented LUT to do this but this is not finished yet.

Other benefit of this alpha transparency is for the blob copy operation that will have a transparency factor. The purpose is to mix the pixels colour values of the blob to copy with the pixels colour values of the screen that receive the blob. That will normally gives a nice effect.

Work on progress ...