Transparent Mode - Samsung S3C2416 User Manual

2D S3C2416X RISC MICROPROCESSOR

4.1.6 Transparent Mode

2D can render image in Transparent Mode. In this mode, the pixels having the same color with background color
(BG_COLOR) are discarded, resulting in a transparent effect. The function of Transparent Mode is illustrated in
the images below, in which the BG_COLOR is set to white.
Figure 18-5. Transparent Mode
2D supports both host-to-screen mode and memory-to-screen mode of BLT.
4.1.7 Known Issue
In the stretch mode (when source image is scaled), the source coordinates are always rounded to the nearest.
This rounding may cause some problem in the boundary when users try to scale the image by integer times. For
example, if user wants to scale the image by four times, and set the X_INCR as 0.25, the source coordinates in
sequence are 0, 0.25, 0.50, 0.75, 1.0 and so on. However, when the current source coordinate is 0.75, it is
rounded to the nearest integer, which is 1, so the first pixel only repeats three times instead of four times. Such
problem may not be an issue when both the source and destination are big pictures or when the scale is not an
integer, but when it comes to small icons or when user wants every pixel to repeat exactly integer times, an
obvious error will occur.
18-6