remove unused ConvertRadiusToSigma from SkBlurMaskFilter

Bug: skia:
Change-Id: I1726f22fc40ad61b1b0485bcda6d383614da1fdb
Reviewed-on: https://skia-review.googlesource.com/113463
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>

1 files changed, 537 insertions, 0 deletions

diff --git a/src/core/SkBlurMask.cpp b/src/core/SkBlurMask.cpp
new file mode 100644
index 0000000000..086977528b
--- /dev/null
+++ b/src/core/SkBlurMask.cpp
@@ -0,0 +1,537 @@
+/*
+ * Copyright 2006 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#include "SkBlurMask.h"
+#include "SkColorPriv.h"
+#include "SkMaskBlurFilter.h"
+#include "SkMath.h"
+#include "SkTemplates.h"
+#include "SkEndian.h"
+
+
+// This constant approximates the scaling done in the software path's
+// "high quality" mode, in SkBlurMask::Blur() (1 / sqrt(3)).
+// IMHO, it actually should be 1:  we blur "less" than we should do
+// according to the CSS and canvas specs, simply because Safari does the same.
+// Firefox used to do the same too, until 4.0 where they fixed it.  So at some
+// point we should probably get rid of these scaling constants and rebaseline
+// all the blur tests.
+static const SkScalar kBLUR_SIGMA_SCALE = 0.57735f;
+
+SkScalar SkBlurMask::ConvertRadiusToSigma(SkScalar radius) {
+    return radius > 0 ? kBLUR_SIGMA_SCALE * radius + 0.5f : 0.0f;
+}
+
+SkScalar SkBlurMask::ConvertSigmaToRadius(SkScalar sigma) {
+    return sigma > 0.5f ? (sigma - 0.5f) / kBLUR_SIGMA_SCALE : 0.0f;
+}
+
+
+static void merge_src_with_blur(uint8_t dst[], int dstRB,
+                                const uint8_t src[], int srcRB,
+                                const uint8_t blur[], int blurRB,
+                                int sw, int sh) {
+    dstRB -= sw;
+    srcRB -= sw;
+    blurRB -= sw;
+    while (--sh >= 0) {
+        for (int x = sw - 1; x >= 0; --x) {
+            *dst = SkToU8(SkAlphaMul(*blur, SkAlpha255To256(*src)));
+            dst += 1;
+            src += 1;
+            blur += 1;
+        }
+        dst += dstRB;
+        src += srcRB;
+        blur += blurRB;
+    }
+}
+
+static void clamp_with_orig(uint8_t dst[], int dstRowBytes,
+                            const uint8_t src[], int srcRowBytes,
+                            int sw, int sh,
+                            SkBlurStyle style) {
+    int x;
+    while (--sh >= 0) {
+        switch (style) {
+        case kSolid_SkBlurStyle:
+            for (x = sw - 1; x >= 0; --x) {
+                int s = *src;
+                int d = *dst;
+                *dst = SkToU8(s + d - SkMulDiv255Round(s, d));
+                dst += 1;
+                src += 1;
+            }
+            break;
+        case kOuter_SkBlurStyle:
+            for (x = sw - 1; x >= 0; --x) {
+                if (*src) {
+                    *dst = SkToU8(SkAlphaMul(*dst, SkAlpha255To256(255 - *src)));
+                }
+                dst += 1;
+                src += 1;
+            }
+            break;
+        default:
+            SkDEBUGFAIL("Unexpected blur style here");
+            break;
+        }
+        dst += dstRowBytes - sw;
+        src += srcRowBytes - sw;
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+// we use a local function to wrap the class static method to work around
+// a bug in gcc98
+void SkMask_FreeImage(uint8_t* image);
+void SkMask_FreeImage(uint8_t* image) {
+    SkMask::FreeImage(image);
+}
+
+bool SkBlurMask::BoxBlur(SkMask* dst, const SkMask& src,
+                         SkScalar sigma, SkBlurStyle style, SkBlurQuality quality,
+                         SkIPoint* margin, bool force_quality) {
+
+    if (src.fFormat != SkMask::kA8_Format) {
+        return false;
+    }
+
+    SkIPoint border;
+
+    SkMaskBlurFilter blurFilter{sigma, sigma};
+    if (blurFilter.hasNoBlur()) {
+        return false;
+    }
+    border = blurFilter.blur(src, dst);
+    // If src.fImage is null, then this call is only to calculate the border.
+    if (src.fImage != nullptr && dst->fImage == nullptr) {
+        return false;
+    }
+
+    if (src.fImage != nullptr) {
+        // if need be, alloc the "real" dst (same size as src) and copy/merge
+        // the blur into it (applying the src)
+        if (style == kInner_SkBlurStyle) {
+            // now we allocate the "real" dst, mirror the size of src
+            size_t srcSize = src.computeImageSize();
+            if (0 == srcSize) {
+                return false;   // too big to allocate, abort
+            }
+            auto blur = dst->fImage;
+            dst->fImage = SkMask::AllocImage(srcSize);
+            auto blurStart = &blur[border.x() + border.y() * dst->fRowBytes];
+            merge_src_with_blur(dst->fImage, src.fRowBytes,
+                                src.fImage, src.fRowBytes,
+                                blurStart,
+                                dst->fRowBytes,
+                                src.fBounds.width(), src.fBounds.height());
+            SkMask::FreeImage(blur);
+        } else if (style != kNormal_SkBlurStyle) {
+            auto dstStart = &dst->fImage[border.x() + border.y() * dst->fRowBytes];
+            clamp_with_orig(dstStart,
+                            dst->fRowBytes, src.fImage, src.fRowBytes,
+                            src.fBounds.width(), src.fBounds.height(), style);
+        }
+    }
+
+    if (style == kInner_SkBlurStyle) {
+        dst->fBounds = src.fBounds; // restore trimmed bounds
+        dst->fRowBytes = src.fRowBytes;
+    }
+
+    if (margin != nullptr) {
+        *margin = border;
+    }
+
+    return true;
+}
+
+/* Convolving a box with itself three times results in a piecewise
+   quadratic function:
+
+   0                              x <= -1.5
+   9/8 + 3/2 x + 1/2 x^2   -1.5 < x <= -.5
+   3/4 - x^2                -.5 < x <= .5
+   9/8 - 3/2 x + 1/2 x^2    0.5 < x <= 1.5
+   0                        1.5 < x
+
+   Mathematica:
+
+   g[x_] := Piecewise [ {
+     {9/8 + 3/2 x + 1/2 x^2 ,  -1.5 < x <= -.5},
+     {3/4 - x^2             ,   -.5 < x <= .5},
+     {9/8 - 3/2 x + 1/2 x^2 ,   0.5 < x <= 1.5}
+   }, 0]
+
+   To get the profile curve of the blurred step function at the rectangle
+   edge, we evaluate the indefinite integral, which is piecewise cubic:
+
+   0                                        x <= -1.5
+   9/16 + 9/8 x + 3/4 x^2 + 1/6 x^3   -1.5 < x <= -0.5
+   1/2 + 3/4 x - 1/3 x^3              -.5 < x <= .5
+   7/16 + 9/8 x - 3/4 x^2 + 1/6 x^3     .5 < x <= 1.5
+   1                                  1.5 < x
+
+   in Mathematica code:
+
+   gi[x_] := Piecewise[ {
+     { 0 , x <= -1.5 },
+     { 9/16 + 9/8 x + 3/4 x^2 + 1/6 x^3, -1.5 < x <= -0.5 },
+     { 1/2 + 3/4 x - 1/3 x^3          ,  -.5 < x <= .5},
+     { 7/16 + 9/8 x - 3/4 x^2 + 1/6 x^3,   .5 < x <= 1.5}
+   },1]
+*/
+
+static float gaussianIntegral(float x) {
+    if (x > 1.5f) {
+        return 0.0f;
+    }
+    if (x < -1.5f) {
+        return 1.0f;
+    }
+
+    float x2 = x*x;
+    float x3 = x2*x;
+
+    if ( x > 0.5f ) {
+        return 0.5625f - (x3 / 6.0f - 3.0f * x2 * 0.25f + 1.125f * x);
+    }
+    if ( x > -0.5f ) {
+        return 0.5f - (0.75f * x - x3 / 3.0f);
+    }
+    return 0.4375f + (-x3 / 6.0f - 3.0f * x2 * 0.25f - 1.125f * x);
+}
+
+/*  ComputeBlurProfile fills in an array of floating
+    point values between 0 and 255 for the profile signature of
+    a blurred half-plane with the given blur radius.  Since we're
+    going to be doing screened multiplications (i.e., 1 - (1-x)(1-y))
+    all the time, we actually fill in the profile pre-inverted
+    (already done 255-x).
+*/
+
+void SkBlurMask::ComputeBlurProfile(uint8_t* profile, int size, SkScalar sigma) {
+    SkASSERT(SkScalarCeilToInt(6*sigma) == size);
+
+    int center = size >> 1;
+
+    float invr = 1.f/(2*sigma);
+
+    profile[0] = 255;
+    for (int x = 1 ; x < size ; ++x) {
+        float scaled_x = (center - x - .5f) * invr;
+        float gi = gaussianIntegral(scaled_x);
+        profile[x] = 255 - (uint8_t) (255.f * gi);
+    }
+}
+
+// TODO MAYBE: Maintain a profile cache to avoid recomputing this for
+// commonly used radii.  Consider baking some of the most common blur radii
+// directly in as static data?
+
+// Implementation adapted from Michael Herf's approach:
+// http://stereopsis.com/shadowrect/
+
+uint8_t SkBlurMask::ProfileLookup(const uint8_t *profile, int loc,
+                                  int blurredWidth, int sharpWidth) {
+    // how far are we from the original edge?
+    int dx = SkAbs32(((loc << 1) + 1) - blurredWidth) - sharpWidth;
+    int ox = dx >> 1;
+    if (ox < 0) {
+        ox = 0;
+    }
+
+    return profile[ox];
+}
+
+void SkBlurMask::ComputeBlurredScanline(uint8_t *pixels, const uint8_t *profile,
+                                        unsigned int width, SkScalar sigma) {
+
+    unsigned int profile_size = SkScalarCeilToInt(6*sigma);
+    SkAutoTMalloc<uint8_t> horizontalScanline(width);
+
+    unsigned int sw = width - profile_size;
+    // nearest odd number less than the profile size represents the center
+    // of the (2x scaled) profile
+    int center = ( profile_size & ~1 ) - 1;
+
+    int w = sw - center;
+
+    for (unsigned int x = 0 ; x < width ; ++x) {
+       if (profile_size <= sw) {
+           pixels[x] = ProfileLookup(profile, x, width, w);
+       } else {
+           float span = float(sw)/(2*sigma);
+           float giX = 1.5f - (x+.5f)/(2*sigma);
+           pixels[x] = (uint8_t) (255 * (gaussianIntegral(giX) - gaussianIntegral(giX + span)));
+       }
+    }
+}
+
+bool SkBlurMask::BlurRect(SkScalar sigma, SkMask *dst,
+                          const SkRect &src, SkBlurStyle style,
+                          SkIPoint *margin, SkMask::CreateMode createMode) {
+    int profileSize = SkScalarCeilToInt(6*sigma);
+    if (profileSize <= 0) {
+        return false;   // no blur to compute
+    }
+
+    int pad = profileSize/2;
+    if (margin) {
+        margin->set( pad, pad );
+    }
+
+    dst->fBounds.set(SkScalarRoundToInt(src.fLeft - pad),
+                     SkScalarRoundToInt(src.fTop - pad),
+                     SkScalarRoundToInt(src.fRight + pad),
+                     SkScalarRoundToInt(src.fBottom + pad));
+
+    dst->fRowBytes = dst->fBounds.width();
+    dst->fFormat = SkMask::kA8_Format;
+    dst->fImage = nullptr;
+
+    int             sw = SkScalarFloorToInt(src.width());
+    int             sh = SkScalarFloorToInt(src.height());
+
+    if (createMode == SkMask::kJustComputeBounds_CreateMode) {
+        if (style == kInner_SkBlurStyle) {
+            dst->fBounds.set(SkScalarRoundToInt(src.fLeft),
+                             SkScalarRoundToInt(src.fTop),
+                             SkScalarRoundToInt(src.fRight),
+                             SkScalarRoundToInt(src.fBottom)); // restore trimmed bounds
+            dst->fRowBytes = sw;
+        }
+        return true;
+    }
+
+    SkAutoTMalloc<uint8_t> profile(profileSize);
+
+    ComputeBlurProfile(profile, profileSize, sigma);
+
+    size_t dstSize = dst->computeImageSize();
+    if (0 == dstSize) {
+        return false;   // too big to allocate, abort
+    }
+
+    uint8_t*        dp = SkMask::AllocImage(dstSize);
+
+    dst->fImage = dp;
+
+    int dstHeight = dst->fBounds.height();
+    int dstWidth = dst->fBounds.width();
+
+    uint8_t *outptr = dp;
+
+    SkAutoTMalloc<uint8_t> horizontalScanline(dstWidth);
+    SkAutoTMalloc<uint8_t> verticalScanline(dstHeight);
+
+    ComputeBlurredScanline(horizontalScanline, profile, dstWidth, sigma);
+    ComputeBlurredScanline(verticalScanline, profile, dstHeight, sigma);
+
+    for (int y = 0 ; y < dstHeight ; ++y) {
+        for (int x = 0 ; x < dstWidth ; x++) {
+            unsigned int maskval = SkMulDiv255Round(horizontalScanline[x], verticalScanline[y]);
+            *(outptr++) = maskval;
+        }
+    }
+
+    if (style == kInner_SkBlurStyle) {
+        // now we allocate the "real" dst, mirror the size of src
+        size_t srcSize = (size_t)(src.width() * src.height());
+        if (0 == srcSize) {
+            return false;   // too big to allocate, abort
+        }
+        dst->fImage = SkMask::AllocImage(srcSize);
+        for (int y = 0 ; y < sh ; y++) {
+            uint8_t *blur_scanline = dp + (y+pad)*dstWidth + pad;
+            uint8_t *inner_scanline = dst->fImage + y*sw;
+            memcpy(inner_scanline, blur_scanline, sw);
+        }
+        SkMask::FreeImage(dp);
+
+        dst->fBounds.set(SkScalarRoundToInt(src.fLeft),
+                         SkScalarRoundToInt(src.fTop),
+                         SkScalarRoundToInt(src.fRight),
+                         SkScalarRoundToInt(src.fBottom)); // restore trimmed bounds
+        dst->fRowBytes = sw;
+
+    } else if (style == kOuter_SkBlurStyle) {
+        for (int y = pad ; y < dstHeight-pad ; y++) {
+            uint8_t *dst_scanline = dp + y*dstWidth + pad;
+            memset(dst_scanline, 0, sw);
+        }
+    } else if (style == kSolid_SkBlurStyle) {
+        for (int y = pad ; y < dstHeight-pad ; y++) {
+            uint8_t *dst_scanline = dp + y*dstWidth + pad;
+            memset(dst_scanline, 0xff, sw);
+        }
+    }
+    // normal and solid styles are the same for analytic rect blurs, so don't
+    // need to handle solid specially.
+
+    return true;
+}
+
+bool SkBlurMask::BlurRRect(SkScalar sigma, SkMask *dst,
+                           const SkRRect &src, SkBlurStyle style,
+                           SkIPoint *margin, SkMask::CreateMode createMode) {
+    // Temporary for now -- always fail, should cause caller to fall back
+    // to old path.  Plumbing just to land API and parallelize effort.
+
+    return false;
+}
+
+// The "simple" blur is a direct implementation of separable convolution with a discrete
+// gaussian kernel.  It's "ground truth" in a sense; too slow to be used, but very
+// useful for correctness comparisons.
+
+bool SkBlurMask::BlurGroundTruth(SkScalar sigma, SkMask* dst, const SkMask& src,
+                                 SkBlurStyle style, SkIPoint* margin) {
+
+    if (src.fFormat != SkMask::kA8_Format) {
+        return false;
+    }
+
+    float variance = sigma * sigma;
+
+    int windowSize = SkScalarCeilToInt(sigma*6);
+    // round window size up to nearest odd number
+    windowSize |= 1;
+
+    SkAutoTMalloc<float> gaussWindow(windowSize);
+
+    int halfWindow = windowSize >> 1;
+
+    gaussWindow[halfWindow] = 1;
+
+    float windowSum = 1;
+    for (int x = 1 ; x <= halfWindow ; ++x) {
+        float gaussian = expf(-x*x / (2*variance));
+        gaussWindow[halfWindow + x] = gaussWindow[halfWindow-x] = gaussian;
+        windowSum += 2*gaussian;
+    }
+
+    // leave the filter un-normalized for now; we will divide by the normalization
+    // sum later;
+
+    int pad = halfWindow;
+    if (margin) {
+        margin->set( pad, pad );
+    }
+
+    dst->fBounds = src.fBounds;
+    dst->fBounds.outset(pad, pad);
+
+    dst->fRowBytes = dst->fBounds.width();
+    dst->fFormat = SkMask::kA8_Format;
+    dst->fImage = nullptr;
+
+    if (src.fImage) {
+
+        size_t dstSize = dst->computeImageSize();
+        if (0 == dstSize) {
+            return false;   // too big to allocate, abort
+        }
+
+        int             srcWidth = src.fBounds.width();
+        int             srcHeight = src.fBounds.height();
+        int             dstWidth = dst->fBounds.width();
+
+        const uint8_t*  srcPixels = src.fImage;
+        uint8_t*        dstPixels = SkMask::AllocImage(dstSize);
+        SkAutoTCallVProc<uint8_t, SkMask_FreeImage> autoCall(dstPixels);
+
+        // do the actual blur.  First, make a padded copy of the source.
+        // use double pad so we never have to check if we're outside anything
+
+        int padWidth = srcWidth + 4*pad;
+        int padHeight = srcHeight;
+        int padSize = padWidth * padHeight;
+
+        SkAutoTMalloc<uint8_t> padPixels(padSize);
+        memset(padPixels, 0, padSize);
+
+        for (int y = 0 ; y < srcHeight; ++y) {
+            uint8_t* padptr = padPixels + y * padWidth + 2*pad;
+            const uint8_t* srcptr = srcPixels + y * srcWidth;
+            memcpy(padptr, srcptr, srcWidth);
+        }
+
+        // blur in X, transposing the result into a temporary floating point buffer.
+        // also double-pad the intermediate result so that the second blur doesn't
+        // have to do extra conditionals.
+
+        int tmpWidth = padHeight + 4*pad;
+        int tmpHeight = padWidth - 2*pad;
+        int tmpSize = tmpWidth * tmpHeight;
+
+        SkAutoTMalloc<float> tmpImage(tmpSize);
+        memset(tmpImage, 0, tmpSize*sizeof(tmpImage[0]));
+
+        for (int y = 0 ; y < padHeight ; ++y) {
+            uint8_t *srcScanline = padPixels + y*padWidth;
+            for (int x = pad ; x < padWidth - pad ; ++x) {
+                float *outPixel = tmpImage + (x-pad)*tmpWidth + y + 2*pad; // transposed output
+                uint8_t *windowCenter = srcScanline + x;
+                for (int i = -pad ; i <= pad ; ++i) {
+                    *outPixel += gaussWindow[pad+i]*windowCenter[i];
+                }
+                *outPixel /= windowSum;
+            }
+        }
+
+        // blur in Y; now filling in the actual desired destination.  We have to do
+        // the transpose again; these transposes guarantee that we read memory in
+        // linear order.
+
+        for (int y = 0 ; y < tmpHeight ; ++y) {
+            float *srcScanline = tmpImage + y*tmpWidth;
+            for (int x = pad ; x < tmpWidth - pad ; ++x) {
+                float *windowCenter = srcScanline + x;
+                float finalValue = 0;
+                for (int i = -pad ; i <= pad ; ++i) {
+                    finalValue += gaussWindow[pad+i]*windowCenter[i];
+                }
+                finalValue /= windowSum;
+                uint8_t *outPixel = dstPixels + (x-pad)*dstWidth + y; // transposed output
+                int integerPixel = int(finalValue + 0.5f);
+                *outPixel = SkClampMax( SkClampPos(integerPixel), 255 );
+            }
+        }
+
+        dst->fImage = dstPixels;
+        // if need be, alloc the "real" dst (same size as src) and copy/merge
+        // the blur into it (applying the src)
+        if (style == kInner_SkBlurStyle) {
+            // now we allocate the "real" dst, mirror the size of src
+            size_t srcSize = src.computeImageSize();
+            if (0 == srcSize) {
+                return false;   // too big to allocate, abort
+            }
+            dst->fImage = SkMask::AllocImage(srcSize);
+            merge_src_with_blur(dst->fImage, src.fRowBytes,
+                srcPixels, src.fRowBytes,
+                dstPixels + pad*dst->fRowBytes + pad,
+                dst->fRowBytes, srcWidth, srcHeight);
+            SkMask::FreeImage(dstPixels);
+        } else if (style != kNormal_SkBlurStyle) {
+            clamp_with_orig(dstPixels + pad*dst->fRowBytes + pad,
+                dst->fRowBytes, srcPixels, src.fRowBytes, srcWidth, srcHeight, style);
+        }
+        (void)autoCall.release();
+    }
+
+    if (style == kInner_SkBlurStyle) {
+        dst->fBounds = src.fBounds; // restore trimmed bounds
+        dst->fRowBytes = src.fRowBytes;
+    }
+
+    return true;
+}