Calculate the 50% scanlines with bit-fiddling.

cybersphinx · cybersphinx · commit 549c476672a9 · 2011-05-06T16:15:01.000+02:00
(cherry picked from commit 4669590)
diff --git a/lib/sequence/sequence.c b/lib/sequence/sequence.c
@@ -356,14 +356,13 @@ static void video_write(bool update)
 				int G = Vclip((A - 100 * U - (C >> 1) + 128) >> 8);
 				int B = Vclip((A + 516 * U + 128) >> 8);
 
-				RGBAframe[rgb_offset] = (B << 16) | (G << 8) | (R << 0) | (0xFF << 24);
+				uint32_t rgba = (B << 16) | (G << 8) | (R << 0) | (0xFF << 24);
+
+				RGBAframe[rgb_offset] = rgba;
 				if (use_scanlines == SCANLINES_50)
 				{
 					// halve the rgb values for a dimmed scanline
-					R /= 2;
-					G /= 2;
-					B /= 2;
-					RGBAframe[rgb_offset + video_width] = (B << 16) | (G << 8) | (R << 0) | (0xff << 24);
+					RGBAframe[rgb_offset + video_width] = (rgba >> 1 & 0x007f7f7f) | 0xff000000;
 				}
 				else if (use_scanlines == SCANLINES_BLACK)
 				{
@@ -379,14 +378,12 @@ static void video_write(bool update)
 				G = Vclip((A - 100 * U - (C >> 1) + 128) >> 8);
 				B = Vclip((A + 516 * U + 128) >> 8);
 
-				RGBAframe[rgb_offset] = (B << 16) | (G << 8) | (R << 0) | (0xFF << 24);
+				rgba = (B << 16) | (G << 8) | (R << 0) | (0xFF << 24);
+				RGBAframe[rgb_offset] = rgba;
 				if (use_scanlines == SCANLINES_50)
 				{
 					// halve the rgb values for a dimmed scanline
-					R /= 2;
-					G /= 2;
-					B /= 2;
-					RGBAframe[rgb_offset + video_width] = (B << 16) | (G << 8) | (R << 0) | (0xff << 24);
+					RGBAframe[rgb_offset + video_width] = (rgba >> 1 & 0x007f7f7f) | 0xff000000;
 				}
 				else if (use_scanlines == SCANLINES_BLACK)
 				{

Original file line number	Diff line number	Diff line change
`@@ -356,14 +356,13 @@ static void video_write(bool update)`
`356`	`356`	`int G = Vclip((A - 100 * U - (C >> 1) + 128) >> 8);`
`357`	`357`	`int B = Vclip((A + 516 * U + 128) >> 8);`
`358`	`358`
`359`		`- RGBAframe[rgb_offset] = (B << 16) \| (G << 8) \| (R << 0) \| (0xFF << 24);`
	`359`	`+ uint32_t rgba = (B << 16) \| (G << 8) \| (R << 0) \| (0xFF << 24);`
	`360`	`+`
	`361`	`+ RGBAframe[rgb_offset] = rgba;`
`360`	`362`	`if (use_scanlines == SCANLINES_50)`
`361`	`363`	`{`
`362`	`364`	`// halve the rgb values for a dimmed scanline`
`363`		`- R /= 2;`
`364`		`- G /= 2;`
`365`		`- B /= 2;`
`366`		`- RGBAframe[rgb_offset + video_width] = (B << 16) \| (G << 8) \| (R << 0) \| (0xff << 24);`
	`365`	`+ RGBAframe[rgb_offset + video_width] = (rgba >> 1 & 0x007f7f7f) \| 0xff000000;`
`367`	`366`	`}`
`368`	`367`	`else if (use_scanlines == SCANLINES_BLACK)`
`369`	`368`	`{`
`@@ -379,14 +378,12 @@ static void video_write(bool update)`
`379`	`378`	`G = Vclip((A - 100 * U - (C >> 1) + 128) >> 8);`
`380`	`379`	`B = Vclip((A + 516 * U + 128) >> 8);`
`381`	`380`
`382`		`- RGBAframe[rgb_offset] = (B << 16) \| (G << 8) \| (R << 0) \| (0xFF << 24);`
	`381`	`+ rgba = (B << 16) \| (G << 8) \| (R << 0) \| (0xFF << 24);`
	`382`	`+ RGBAframe[rgb_offset] = rgba;`
`383`	`383`	`if (use_scanlines == SCANLINES_50)`
`384`	`384`	`{`
`385`	`385`	`// halve the rgb values for a dimmed scanline`
`386`		`- R /= 2;`
`387`		`- G /= 2;`
`388`		`- B /= 2;`
`389`		`- RGBAframe[rgb_offset + video_width] = (B << 16) \| (G << 8) \| (R << 0) \| (0xff << 24);`
	`386`	`+ RGBAframe[rgb_offset + video_width] = (rgba >> 1 & 0x007f7f7f) \| 0xff000000;`
`390`	`387`	`}`
`391`	`388`	`else if (use_scanlines == SCANLINES_BLACK)`
`392`	`389`	`{`