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Use fixed point math for the inner loop of ZoomSurface(). This gives a huge speedup on PowerPC.

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Note that 16777216=2^24 is 1.0 in U(8,24) fixed point and 8388608=2^23 is 0.5. Also, single precision IEEE floating point has 23 bits of mantissa and U(8,24) has 24 bits of fraction so no precision is lost.
This commit is contained in:
Steve Checkoway
2007-10-27 16:36:54 +00:00
parent 4f3724c550
commit 1b96c0da14
1 changed files with 17 additions and 16 deletions
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stepmania/src/RageSurfaceUtils_Zoom.cpp
+17 -16
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@@ -16,7 +16,7 @@ using namespace std;
* lines.)
*/
static void InitVectors( vector<int> &s0, vector<int> &s1, vector<float> &percent, int src, int dst )
static void InitVectors( vector<int> &s0, vector<int> &s1, vector<uint32_t> &percent, int src, int dst )
{
if( src >= dst )
{
@@ -28,12 +28,12 @@ static void InitVectors( vector<int> &s0, vector<int> &s1, vector<float> &percen
* going 512->256, then dst[0] should come from the pixels from 0..1 and
* 1..2, so sax[0] is 1. sx is the total number of pixels, so sx/2 is the
* distance from the start of the sample to its center. */
const float sax = sx*x + sx/2;
const float sax = sx*x + sx/2.0f;
/* sx/2 is the distance from the start of the sample to the center;
* sx/4 is the distance from the center of the sample to the center of
* either pixel. */
const float xstep = sx/4;
const float xstep = sx/4.0f;
/* source x coordinates of left and right pixels to sample */
s0.push_back(int(sax-xstep));
@@ -43,7 +43,7 @@ static void InitVectors( vector<int> &s0, vector<int> &s1, vector<float> &percen
{
/* If the sampled pixels happen to be the same, the distance
* will be 0. Avoid division by zero. */
percent.push_back( 1.f );
percent.push_back( 1<<24 );
} else {
const int xdist = s1[x] - s0[x];
@@ -52,8 +52,8 @@ static void InitVectors( vector<int> &s0, vector<int> &s1, vector<float> &percen
/* sax is somewhere between the centers of both sampled
* pixels; find the percentage: */
const float p = (sax - fleft) / xdist;
percent.push_back(1-p);
const float p = (1.0f - (sax - fleft) / xdist) * 16777216.0f;
percent.push_back( uint32_t(p) );
}
}
}
@@ -77,8 +77,8 @@ static void InitVectors( vector<int> &s0, vector<int> &s1, vector<float> &percen
s0.push_back( clamp(int(sax), 0, src-1));
s1.push_back( clamp(int(sax+1), 0, src-1) );
const float p = 1 - (sax - floorf(sax));
percent.push_back( p );
const float p = (1.0f - (sax - floorf(sax))) * 16777216.0f;
percent.push_back( uint32_t(p) );
}
}
}
@@ -88,7 +88,7 @@ static void ZoomSurface( const RageSurface * src, RageSurface * dst )
/* For each destination coordinate, two source rows, two source columns
* and the percentage of the first row and first column: */
vector<int> esx0, esx1, esy0, esy1;
vector<float> ex0, ey0;
vector<uint32_t> ex0, ey0;
InitVectors( esx0, esx1, ex0, src->w, dst->w );
InitVectors( esy0, esy1, ey0, src->h, dst->h );
@@ -114,13 +114,14 @@ static void ZoomSurface( const RageSurface * src, RageSurface * dst )
uint8_t color[4];
for( int c = 0; c < 4; ++c )
{
float x0, x1;
x0 = c00[c] * ex0[x];
x0 += c01[c] * (1-ex0[x]);
x1 = c10[c] * ex0[x];
x1 += c11[c] * (1-ex0[x]);
const float res = (x0 * ey0[y]) + (x1 * (1-ey0[y])) + 0.5f;
uint32_t x0 = uint32_t(c00[c]) * ex0[x];
x0 += uint32_t(c01[c]) * (16777216 - ex0[x]);
x0 >>= 24;
uint32_t x1 = uint32_t(c10[c]) * ex0[x];
x1 += uint32_t(c11[c]) * (16777216 - ex0[x]);
x1 >>= 24;
const uint32_t res = ((x0 * ey0[y]) + (x1 * (16777216-ey0[y])) + 8388608) >> 24;
color[c] = uint8_t(res);
}
*dp = *(uint32_t *) color;