More general version of image filtering; reworked to be robust and easier to SSE

src/core/SkBitmapProcBicubic.cpp

-/*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkBitmapProcState.h"
-#include "SkBitmap.h"
-#include "SkColor.h"
-#include "SkColorPriv.h"
-#include "SkUnPreMultiply.h"
-#include "SkRTConf.h"
-#include "SkShader.h"
-
-#define DS(x) SkDoubleToScalar(x)
-
-#define MUL(a, b)   ((a) * (b))
-
-static inline SkPMColor cubicBlend(const SkFixed cc[4], SkPMColor c0, SkPMColor c1, SkPMColor c2, SkPMColor c3) {
-    SkFixed fa = MUL(cc[0], SkGetPackedA32(c0)) + MUL(cc[1], SkGetPackedA32(c1)) + MUL(cc[2], SkGetPackedA32(c2)) + MUL(cc[3], SkGetPackedA32(c3));
-    SkFixed fr = MUL(cc[0], SkGetPackedR32(c0)) + MUL(cc[1], SkGetPackedR32(c1)) + MUL(cc[2], SkGetPackedR32(c2)) + MUL(cc[3], SkGetPackedR32(c3));
-    SkFixed fg = MUL(cc[0], SkGetPackedG32(c0)) + MUL(cc[1], SkGetPackedG32(c1)) + MUL(cc[2], SkGetPackedG32(c2)) + MUL(cc[3], SkGetPackedG32(c3));
-    SkFixed fb = MUL(cc[0], SkGetPackedB32(c0)) + MUL(cc[1], SkGetPackedB32(c1)) + MUL(cc[2], SkGetPackedB32(c2)) + MUL(cc[3], SkGetPackedB32(c3));
-
-    int a = SkClampMax(SkFixedRoundToInt(fa), 255);
-    int r = SkClampMax(SkFixedRoundToInt(fr), a);
-    int g = SkClampMax(SkFixedRoundToInt(fg), a);
-    int b = SkClampMax(SkFixedRoundToInt(fb), a);
-
-    return SkPackARGB32(a, r, g, b);
-}
-
-static float poly_eval(const float cc[4], float t) {
-    return cc[0] + t * (cc[1] + t * (cc[2] + t * cc[3]));
-}
-
-static void build_coeff4(SkFixed dst[4], float t) {
-    static const SkScalar coefficients[16] = {
-        DS( 1.0 / 18.0), DS(-9.0 / 18.0), DS( 15.0 / 18.0), DS( -7.0 / 18.0),
-        DS(16.0 / 18.0), DS( 0.0 / 18.0), DS(-36.0 / 18.0), DS( 21.0 / 18.0),
-        DS( 1.0 / 18.0), DS( 9.0 / 18.0), DS( 27.0 / 18.0), DS(-21.0 / 18.0),
-        DS( 0.0 / 18.0), DS( 0.0 / 18.0), DS( -6.0 / 18.0), DS(  7.0 / 18.0),
-    };
-
-    dst[0] = SkFloatToFixed(poly_eval(&coefficients[ 0], t));
-    dst[1] = SkFloatToFixed(poly_eval(&coefficients[ 4], t));
-    dst[2] = SkFloatToFixed(poly_eval(&coefficients[ 8], t));
-    dst[3] = SkFloatToFixed(poly_eval(&coefficients[12], t));
-}
-
-static SkPMColor doBicubicFilter(const SkBitmap *bm, SkFixed coeffX[4], SkFixed coeffY[4],
-                            int x0, int x1, int x2, int x3,
-                            int y0, int y1, int y2, int y3 )
-{
-    SkPMColor s00 = *bm->getAddr32(x0, y0);
-    SkPMColor s10 = *bm->getAddr32(x1, y0);
-    SkPMColor s20 = *bm->getAddr32(x2, y0);
-    SkPMColor s30 = *bm->getAddr32(x3, y0);
-    SkPMColor s0 = cubicBlend(coeffX, s00, s10, s20, s30);
-    SkPMColor s01 = *bm->getAddr32(x0, y1);
-    SkPMColor s11 = *bm->getAddr32(x1, y1);
-    SkPMColor s21 = *bm->getAddr32(x2, y1);
-    SkPMColor s31 = *bm->getAddr32(x3, y1);
-    SkPMColor s1 = cubicBlend(coeffX, s01, s11, s21, s31);
-    SkPMColor s02 = *bm->getAddr32(x0, y2);
-    SkPMColor s12 = *bm->getAddr32(x1, y2);
-    SkPMColor s22 = *bm->getAddr32(x2, y2);
-    SkPMColor s32 = *bm->getAddr32(x3, y2);
-    SkPMColor s2 = cubicBlend(coeffX, s02, s12, s22, s32);
-    SkPMColor s03 = *bm->getAddr32(x0, y3);
-    SkPMColor s13 = *bm->getAddr32(x1, y3);
-    SkPMColor s23 = *bm->getAddr32(x2, y3);
-    SkPMColor s33 = *bm->getAddr32(x3, y3);
-    SkPMColor s3 = cubicBlend(coeffX, s03, s13, s23, s33);
-    return cubicBlend(coeffY, s0, s1, s2, s3);
-}
-
-static void bicubicFilter(const SkBitmapProcState& s, int x, int y,
-                          SkPMColor* SK_RESTRICT colors, int count) {
-
-    const int maxX = s.fBitmap->width() - 1;
-    const int maxY = s.fBitmap->height() - 1;
-
-    while (count-- > 0) {
-        SkPoint srcPt;
-        s.fInvProc(*s.fInvMatrix, SkIntToScalar(x),
-                    SkIntToScalar(y), &srcPt);
-        srcPt.fX -= SK_ScalarHalf;
-        srcPt.fY -= SK_ScalarHalf;
-        SkScalar fractx = srcPt.fX - SkScalarFloorToScalar(srcPt.fX);
-        SkScalar fracty = srcPt.fY - SkScalarFloorToScalar(srcPt.fY);
-
-        SkFixed coeffX[4], coeffY[4];
-        build_coeff4(coeffX, fractx);
-        build_coeff4(coeffY, fracty);
-
-        int sx = SkScalarFloorToInt(srcPt.fX);
-        int sy = SkScalarFloorToInt(srcPt.fY);
-
-        // Here is where we can support other tile modes (e.g. repeat or mirror)
-        int x0 = SkClampMax(sx - 1, maxX);
-        int x1 = SkClampMax(sx    , maxX);
-        int x2 = SkClampMax(sx + 1, maxX);
-        int x3 = SkClampMax(sx + 2, maxX);
-        int y0 = SkClampMax(sy - 1, maxY);
-        int y1 = SkClampMax(sy    , maxY);
-        int y2 = SkClampMax(sy + 1, maxY);
-        int y3 = SkClampMax(sy + 2, maxY);
-
-        *colors++ = doBicubicFilter( s.fBitmap, coeffX, coeffY, x0, x1, x2, x3, y0, y1, y2, y3 );
-
-        x++;
-    }
-}
-
-static void bicubicFilter_ScaleOnly(const SkBitmapProcState &s, int x, int y,
-                                    SkPMColor *SK_RESTRICT colors, int count) {
-    const int maxX = s.fBitmap->width() - 1;
-    const int maxY = s.fBitmap->height() - 1;
-
-    SkPoint srcPt;
-    s.fInvProc(*s.fInvMatrix, SkIntToScalar(x), SkIntToScalar(y), &srcPt);
-    srcPt.fY -= SK_ScalarHalf;
-    SkScalar fracty = srcPt.fY - SkScalarFloorToScalar(srcPt.fY);
-    SkFixed coeffX[4], coeffY[4];
-    build_coeff4(coeffY, fracty);
-    int sy = SkScalarFloorToInt(srcPt.fY);
-    int y0 = SkClampMax(sy - 1, maxY);
-    int y1 = SkClampMax(sy    , maxY);
-    int y2 = SkClampMax(sy + 1, maxY);
-    int y3 = SkClampMax(sy + 2, maxY);
-
-    while (count-- > 0) {
-        s.fInvProc(*s.fInvMatrix, SkIntToScalar(x), SkIntToScalar(y), &srcPt);
-        srcPt.fX -= SK_ScalarHalf;
-        SkScalar fractx = srcPt.fX - SkScalarFloorToScalar(srcPt.fX);
-
-        build_coeff4(coeffX, fractx);
-
-        int sx = SkScalarFloorToInt(srcPt.fX);
-
-        // Here is where we can support other tile modes (e.g. repeat or mirror)
-        int x0 = SkClampMax(sx - 1, maxX);
-        int x1 = SkClampMax(sx    , maxX);
-        int x2 = SkClampMax(sx + 1, maxX);
-        int x3 = SkClampMax(sx + 2, maxX);
-
-        *colors++ = doBicubicFilter( s.fBitmap, coeffX, coeffY, x0, x1, x2, x3, y0, y1, y2, y3 );
-
-        x++;
-    }
-}
-
-SkBitmapProcState::ShaderProc32
-SkBitmapProcState::chooseBicubicFilterProc(const SkPaint& paint) {
-    // we need to be requested
-    uint32_t mask = SkPaint::kFilterBitmap_Flag
-                  | SkPaint::kBicubicFilterBitmap_Flag
-                  ;
-    if ((paint.getFlags() & mask) != mask) {
-        return NULL;
-    }
-
-    // TODO: consider supporting other configs (e.g. 565, A8)
-    if (fBitmap->config() != SkBitmap::kARGB_8888_Config) {
-        return NULL;
-    }
-
-    // TODO: consider supporting repeat and mirror
-    if (SkShader::kClamp_TileMode != fTileModeX || SkShader::kClamp_TileMode != fTileModeY) {
-        return NULL;
-    }
-
-    // TODO: support blending inside our procs
-    if (0xFF != paint.getAlpha()) {
-        return NULL;
-    }
-
-    if (fInvType & SkMatrix::kAffine_Mask) {
-        return bicubicFilter;
-    } else if (fInvType & SkMatrix::kScale_Mask) {
-        return bicubicFilter_ScaleOnly;
-    } else {
-        return NULL;
-    }
-}