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* 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.
#ifndef SkBlurMask_DEFINED
#define SkBlurMask_DEFINED
#include "SkBlurTypes.h"
#include "SkShader.h"
#include "SkMask.h"
#include "SkRRect.h"
class SkBlurMask {
static bool SK_WARN_UNUSED_RESULT BlurRect(SkScalar sigma, SkMask *dst, const SkRect &src,
SkBlurStyle, SkIPoint *margin = nullptr,
SkMask::CreateMode createMode =
static bool SK_WARN_UNUSED_RESULT BlurRRect(SkScalar sigma, SkMask *dst, const SkRRect &src,
SkBlurStyle, SkIPoint *margin = nullptr,
SkMask::CreateMode createMode =
// forceQuality will prevent BoxBlur from falling back to the low quality approach when sigma
// is very small -- this can be used predict the margin bump ahead of time without completely
// replicating the internal logic. This permits not only simpler caching of blurred results,
// but also being able to predict precisely at what pixels the blurred profile of e.g. a
// rectangle will lie.
static bool SK_WARN_UNUSED_RESULT BoxBlur(SkMask* dst, const SkMask& src,
SkScalar sigma, SkBlurStyle style, SkBlurQuality,
SkIPoint* margin = nullptr,
bool forceQuality = false);
// the "ground truth" blur does a gaussian convolution; it's slow
// but useful for comparison purposes.
static bool SK_WARN_UNUSED_RESULT BlurGroundTruth(SkScalar sigma, SkMask* dst,
const SkMask& src,
SkBlurStyle, SkIPoint* margin = nullptr);
// If radius > 0, return the corresponding sigma, else return 0
static SkScalar ConvertRadiusToSigma(SkScalar radius);
// If sigma > 0.5, return the corresponding radius, else return 0
static SkScalar ConvertSigmaToRadius(SkScalar sigma);
/* Helper functions for analytic rectangle blurs */
/** Look up the intensity of the (one dimnensional) blurred half-plane.
@param profile The precomputed 1D blur profile; memory allocated by and managed by
ComputeBlurProfile below.
@param loc the location to look up; The lookup will clamp invalid inputs, but
meaningful data are available between 0 and blurred_width
@param blurred_width The width of the final, blurred rectangle
@param sharp_width The width of the original, unblurred rectangle.
static uint8_t ProfileLookup(const uint8_t* profile, int loc, int blurredWidth, int sharpWidth);
/** Allocate memory for and populate the profile of a 1D blurred halfplane. The caller
must free the memory. The amount of memory allocated will be exactly 6*sigma bytes.
@param sigma The standard deviation of the gaussian blur kernel
static uint8_t* ComputeBlurProfile(SkScalar sigma);
/** Compute an entire scanline of a blurred step function. This is a 1D helper that
will produce both the horizontal and vertical profiles of the blurry rectangle.
@param pixels Location to store the resulting pixel data; allocated and managed by caller
@param profile Precomputed blur profile computed by ComputeBlurProfile above.
@param width Size of the pixels array.
@param sigma Standard deviation of the gaussian blur kernel used to compute the profile;
this implicitly gives the size of the pixels array.
static void ComputeBlurredScanline(uint8_t* pixels, const uint8_t* profile,
unsigned int width, SkScalar sigma);