SkM44.cpp File Reference

#include "include/core/SkM44.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkRect.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkFloatingPoint.h"
#include "src/base/SkVx.h"
#include "src/core/SkMatrixInvert.h"
#include "src/core/SkMatrixPriv.h"
#include "src/core/SkPathPriv.h"

Go to the source code of this file.

Functions
static void	transpose_arrays (SkScalar dst[], const SkScalar src[])
static SkRect	map_rect_affine (const SkRect &src, const float mat[16])
static SkRect	map_rect_perspective (const SkRect &src, const float mat[16])
static SkV3	normalize (SkV3 v)
static SkV4	v4 (SkV3 v, SkScalar w)

Function Documentation

map_rect_affine()

static SkRect map_rect_affine ( const SkRect &  src, const float  mat[16]  )

static

Definition at line 140 of file SkM44.cpp.

                                                                      {
    // When multiplied against vectors of the form <x,y,x,y>, 'flip' allows a single min()
    // to compute both the min and "negated" max between the xy coordinates. Once finished, another
    // multiplication produces the original max.
    const skvx::float4 flip{1.f, 1.f, -1.f, -1.f};
 
    // Since z = 0 and it's assumed ther's no perspective, only load the upper 2x2 and (tx,ty) in c3
    auto c0 = skvx::shuffle<0,1,0,1>(skvx::float2::Load(mat + 0)) * flip;
    auto c1 = skvx::shuffle<0,1,0,1>(skvx::float2::Load(mat + 4)) * flip;
    auto c3 = skvx::shuffle<0,1,0,1>(skvx::float2::Load(mat + 12));
 
    // Compute the min and max of the four transformed corners pre-translation; then translate once
    // at the end.
    auto minMax = c3 + flip * min(min(c0 * src.fLeft  + c1 * src.fTop,
                                      c0 * src.fRight + c1 * src.fTop),
                                  min(c0 * src.fLeft  + c1 * src.fBottom,
                                      c0 * src.fRight + c1 * src.fBottom));
 
    // minMax holds (min x, min y, max x, max y) so can be copied into an SkRect expecting l,t,r,b
    SkRect r;
    minMax.store(&r);
    return r;
}

map_rect_perspective()

static SkRect map_rect_perspective ( const SkRect &  src, const float  mat[16]  )

static

Definition at line 164 of file SkM44.cpp.

                                                                           {
    // Like map_rect_affine, z = 0 so we can skip the 3rd column, but we do need to compute w's
    // for each corner of the src rect.
    auto c0 = skvx::float4::Load(mat + 0);
    auto c1 = skvx::float4::Load(mat + 4);
    auto c3 = skvx::float4::Load(mat + 12);
 
    // Unlike map_rect_affine, we do not defer the 4th column since we may need to homogeneous
    // coordinates to clip against the w=0 plane
    auto tl = c0 * src.fLeft  + c1 * src.fTop    + c3;
    auto tr = c0 * src.fRight + c1 * src.fTop    + c3;
    auto bl = c0 * src.fLeft  + c1 * src.fBottom + c3;
    auto br = c0 * src.fRight + c1 * src.fBottom + c3;
 
    // After clipping to w>0 and projecting to 2d, 'project' employs the same negation trick to
    // compute min and max at the same time.
    const skvx::float4 flip{1.f, 1.f, -1.f, -1.f};
    auto project = [&flip](const skvx::float4& p0, const skvx::float4& p1, const skvx::float4& p2) {
        float w0 = p0[3];
        if (w0 >= SkPathPriv::kW0PlaneDistance) {
            // Unclipped, just divide by w
            return flip * skvx::shuffle<0,1,0,1>(p0) / w0;
        } else {
            auto clip = [&](const skvx::float4& p) {
                float w = p[3];
                if (w >= SkPathPriv::kW0PlaneDistance) {
                    float t = (SkPathPriv::kW0PlaneDistance - w0) / (w - w0);
                    auto c = (t * skvx::shuffle<0,1>(p) + (1.f - t) * skvx::shuffle<0,1>(p0)) /
                                  SkPathPriv::kW0PlaneDistance;
 
                    return flip * skvx::shuffle<0,1,0,1>(c);
                } else {
                    return skvx::float4(SK_ScalarInfinity);
                }
            };
            // Clip both edges leaving p0, and return the min/max of the two clipped points
            // (since clip returns infinity when both p0 and 2nd vertex have w<0, it'll
            // automatically be ignored).
            return min(clip(p1), clip(p2));
        }
    };
 
    // Project all 4 corners, and pass in their adjacent vertices for clipping if it has w < 0,
    // then accumulate the min and max xy's.
    auto minMax = flip * min(min(project(tl, tr, bl), project(tr, br, tl)),
                             min(project(br, bl, tr), project(bl, tl, br)));
 
    SkRect r;
    minMax.store(&r);
    return r;
}

normalize()

static SkV3 normalize ( SkV3  v )

static

Definition at line 323 of file SkM44.cpp.

                              {
    const auto vlen = v.length();
 
    return SkScalarNearlyZero(vlen) ? v : v * (1.0f / vlen);
}

transpose_arrays()

static void transpose_arrays ( SkScalar  dst[], const SkScalar  src[]  )

static

Definition at line 37 of file SkM44.cpp.

                                                                   {
    dst[0]  = src[0]; dst[1]  = src[4]; dst[2]  = src[8];  dst[3]  = src[12];
    dst[4]  = src[1]; dst[5]  = src[5]; dst[6]  = src[9];  dst[7]  = src[13];
    dst[8]  = src[2]; dst[9]  = src[6]; dst[10] = src[10]; dst[11] = src[14];
    dst[12] = src[3]; dst[13] = src[7]; dst[14] = src[11]; dst[15] = src[15];
}

v4()

static SkV4 v4 ( SkV3  v, SkScalar  w  )

static

Definition at line 329 of file SkM44.cpp.

{ return {v.x, v.y, v.z, w}; }