SkEdge.cpp File Reference

#include "src/core/SkEdge.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkTo.h"
#include "src/base/SkMathPriv.h"
#include "src/core/SkFDot6.h"
#include <algorithm>
#include <utility>

Go to the source code of this file.

Macros
#define	MAX_COEFF_SHIFT   6

Functions
static SkFixed	SkFDot6ToFixedDiv2 (SkFDot6 value)
static SkFDot6	cheap_distance (SkFDot6 dx, SkFDot6 dy)
static int	diff_to_shift (SkFDot6 dx, SkFDot6 dy, int shiftAA=2)
static int	SkFDot6UpShift (SkFDot6 x, int upShift)
static SkFDot6	cubic_delta_from_line (SkFDot6 a, SkFDot6 b, SkFDot6 c, SkFDot6 d)

Macro Definition Documentation

MAX_COEFF_SHIFT

#define MAX_COEFF_SHIFT   6

Definition at line 171 of file SkEdge.cpp.

Function Documentation

cheap_distance()

static SkFDot6 cheap_distance ( SkFDot6  dx, SkFDot6  dy  )

inlinestatic

Definition at line 173 of file SkEdge.cpp.

{
    dx = SkAbs32(dx);
    dy = SkAbs32(dy);
    // return max + min/2
    if (dx > dy)
        dx += dy >> 1;
    else
        dx = dy + (dx >> 1);
    return dx;
}

cubic_delta_from_line()

static SkFDot6 cubic_delta_from_line ( SkFDot6  a, SkFDot6  b, SkFDot6  c, SkFDot6  d  )

static

Definition at line 364 of file SkEdge.cpp.

{
    // since our parameters may be negative, we don't use << to avoid ASAN warnings
    SkFDot6 oneThird = (a*8 - b*15 + 6*c + d) * 19 >> 9;
    SkFDot6 twoThird = (a + 6*b - c*15 + d*8) * 19 >> 9;
 
    return std::max(SkAbs32(oneThird), SkAbs32(twoThird));
}

diff_to_shift()

static int diff_to_shift ( SkFDot6  dx, SkFDot6  dy, int  shiftAA = 2  )

inlinestatic

Definition at line 185 of file SkEdge.cpp.

{
    // cheap calc of distance from center of p0-p2 to the center of the curve
    SkFDot6 dist = cheap_distance(dx, dy);
 
    // shift down dist (it is currently in dot6)
    // down by 3 should give us 1/8 pixel accuracy (assuming our dist is accurate...)
    // this is chosen by heuristic: make it as big as possible (to minimize segments)
    // ... but small enough so that our curves still look smooth
    // When shift > 0, we're using AA and everything is scaled up so we can
    // lower the accuracy.
    dist = (dist + (1 << (2 + shiftAA))) >> (3 + shiftAA);
 
    // each subdivision (shift value) cuts this dist (error) by 1/4
    return (32 - SkCLZ(dist)) >> 1;
}

SkFDot6ToFixedDiv2()

static SkFixed SkFDot6ToFixedDiv2 ( SkFDot6  value )

inlinestatic

Definition at line 30 of file SkEdge.cpp.

                                                        {
    // we want to return SkFDot6ToFixed(value >> 1), but we don't want to throw
    // away data in value, so just perform a modify up-shift
    return SkLeftShift(value, 16 - 6 - 1);
}

SkFDot6UpShift()

static int SkFDot6UpShift ( SkFDot6  x, int  upShift  )

inlinestatic

Definition at line 351 of file SkEdge.cpp.

                                                         {
    SkASSERT((SkLeftShift(x, upShift) >> upShift) == x);
    return SkLeftShift(x, upShift);
}