Use lookup tables for pixel upconversion
You have to loop many times when converting e.g. 2 bits to 8,
so have a couple of lookup tables to speed things up. We still
use bit replication to get from 8 bits to 16 bits though.
diff --git a/common/rfb/PixelFormat.inl b/common/rfb/PixelFormat.inl
index 4bc4a70..f9fb125 100644
--- a/common/rfb/PixelFormat.inl
+++ b/common/rfb/PixelFormat.inl
@@ -102,55 +102,33 @@
inline void PixelFormat::rgbFromPixel(Pixel p, rdr::U16 *r, rdr::U16 *g, rdr::U16 *b) const
{
- int mb, rb, gb, bb;
+ rdr::U8 _r, _g, _b;
- /* Bit replication is much cheaper than multiplication and division */
+ _r = p >> redShift;
+ _g = p >> greenShift;
+ _b = p >> blueShift;
- mb = minBits;
- rb = redBits;
- gb = greenBits;
- bb = blueBits;
+ _r = upconvTable[(redBits-1)*256 + _r];
+ _g = upconvTable[(greenBits-1)*256 + _g];
+ _b = upconvTable[(blueBits-1)*256 + _b];
- *r = (p >> redShift) << (16 - rb);
- *g = (p >> greenShift) << (16 - gb);
- *b = (p >> blueShift) << (16 - bb);
-
- while (mb < 16) {
- *r = *r | (*r >> rb);
- *g = *g | (*g >> gb);
- *b = *b | (*b >> bb);
- mb <<= 1;
- rb <<= 1;
- gb <<= 1;
- bb <<= 1;
- }
+ *r = _r << 8 | _r;
+ *g = _g << 8 | _g;
+ *b = _b << 8 | _b;
}
inline void PixelFormat::rgbFromPixel(Pixel p, rdr::U8 *r, rdr::U8 *g, rdr::U8 *b) const
{
- int mb, rb, gb, bb;
+ rdr::U8 _r, _g, _b;
- /* Bit replication is much cheaper than multiplication and division */
+ _r = p >> redShift;
+ _g = p >> greenShift;
+ _b = p >> blueShift;
- mb = minBits;
- rb = redBits;
- gb = greenBits;
- bb = blueBits;
-
- *r = (p >> redShift) << (8 - rb);
- *g = (p >> greenShift) << (8 - gb);
- *b = (p >> blueShift) << (8 - bb);
-
- while (mb < 8) {
- *r = *r | (*r >> rb);
- *g = *g | (*g >> gb);
- *b = *b | (*b >> bb);
- mb <<= 1;
- rb <<= 1;
- gb <<= 1;
- bb <<= 1;
- }
+ *r = upconvTable[(redBits-1)*256 + _r];
+ *g = upconvTable[(greenBits-1)*256 + _g];
+ *b = upconvTable[(blueBits-1)*256 + _b];
}