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gecko/gfx/2d/Blur.cpp

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/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla gfx.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include "mozilla/gfx/Blur.h"
#include <algorithm>
#include <math.h>
#include <string.h>
#include "CheckedInt.h"
#include "mozilla/Util.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
using namespace std;
namespace mozilla {
namespace gfx {
/**
* Box blur involves looking at one pixel, and setting its value to the average
* of its neighbouring pixels.
* @param aInput The input buffer.
* @param aOutput The output buffer.
* @param aLeftLobe The number of pixels to blend on the left.
* @param aRightLobe The number of pixels to blend on the right.
* @param aWidth The number of columns in the buffers.
* @param aRows The number of rows in the buffers.
* @param aSkipRect An area to skip blurring in.
* XXX shouldn't we pass stride in separately here?
*/
static void
BoxBlurHorizontal(unsigned char* aInput,
unsigned char* aOutput,
int32_t aLeftLobe,
int32_t aRightLobe,
int32_t aWidth,
int32_t aRows,
const IntRect& aSkipRect)
{
MOZ_ASSERT(aWidth > 0);
int32_t boxSize = aLeftLobe + aRightLobe + 1;
bool skipRectCoversWholeRow = 0 >= aSkipRect.x &&
aWidth <= aSkipRect.XMost();
for (int32_t y = 0; y < aRows; y++) {
// Check whether the skip rect intersects this row. If the skip
// rect covers the whole surface in this row, we can avoid
// this row entirely (and any others along the skip rect).
bool inSkipRectY = y >= aSkipRect.y &&
y < aSkipRect.YMost();
if (inSkipRectY && skipRectCoversWholeRow) {
y = aSkipRect.YMost() - 1;
continue;
}
int32_t alphaSum = 0;
for (int32_t i = 0; i < boxSize; i++) {
int32_t pos = i - aLeftLobe;
// See assertion above; if aWidth is zero, then we would have no
// valid position to clamp to.
pos = max(pos, 0);
pos = min(pos, aWidth - 1);
alphaSum += aInput[aWidth * y + pos];
}
for (int32_t x = 0; x < aWidth; x++) {
// Check whether we are within the skip rect. If so, go
// to the next point outside the skip rect.
if (inSkipRectY && x >= aSkipRect.x &&
x < aSkipRect.XMost()) {
x = aSkipRect.XMost();
if (x >= aWidth)
break;
// Recalculate the neighbouring alpha values for
// our new point on the surface.
alphaSum = 0;
for (int32_t i = 0; i < boxSize; i++) {
int32_t pos = x + i - aLeftLobe;
// See assertion above; if aWidth is zero, then we would have no
// valid position to clamp to.
pos = max(pos, 0);
pos = min(pos, aWidth - 1);
alphaSum += aInput[aWidth * y + pos];
}
}
int32_t tmp = x - aLeftLobe;
int32_t last = max(tmp, 0);
int32_t next = min(tmp + boxSize, aWidth - 1);
aOutput[aWidth * y + x] = alphaSum / boxSize;
alphaSum += aInput[aWidth * y + next] -
aInput[aWidth * y + last];
}
}
}
/**
* Identical to BoxBlurHorizontal, except it blurs top and bottom instead of
* left and right.
* XXX shouldn't we pass stride in separately here?
*/
static void
BoxBlurVertical(unsigned char* aInput,
unsigned char* aOutput,
int32_t aTopLobe,
int32_t aBottomLobe,
int32_t aWidth,
int32_t aRows,
const IntRect& aSkipRect)
{
MOZ_ASSERT(aRows > 0);
int32_t boxSize = aTopLobe + aBottomLobe + 1;
bool skipRectCoversWholeColumn = 0 >= aSkipRect.y &&
aRows <= aSkipRect.YMost();
for (int32_t x = 0; x < aWidth; x++) {
bool inSkipRectX = x >= aSkipRect.x &&
x < aSkipRect.XMost();
if (inSkipRectX && skipRectCoversWholeColumn) {
x = aSkipRect.XMost() - 1;
continue;
}
int32_t alphaSum = 0;
for (int32_t i = 0; i < boxSize; i++) {
int32_t pos = i - aTopLobe;
// See assertion above; if aRows is zero, then we would have no
// valid position to clamp to.
pos = max(pos, 0);
pos = min(pos, aRows - 1);
alphaSum += aInput[aWidth * pos + x];
}
for (int32_t y = 0; y < aRows; y++) {
if (inSkipRectX && y >= aSkipRect.y &&
y < aSkipRect.YMost()) {
y = aSkipRect.YMost();
if (y >= aRows)
break;
alphaSum = 0;
for (int32_t i = 0; i < boxSize; i++) {
int32_t pos = y + i - aTopLobe;
// See assertion above; if aRows is zero, then we would have no
// valid position to clamp to.
pos = max(pos, 0);
pos = min(pos, aRows - 1);
alphaSum += aInput[aWidth * pos + x];
}
}
int32_t tmp = y - aTopLobe;
int32_t last = max(tmp, 0);
int32_t next = min(tmp + boxSize, aRows - 1);
aOutput[aWidth * y + x] = alphaSum/boxSize;
alphaSum += aInput[aWidth * next + x] -
aInput[aWidth * last + x];
}
}
}
static void ComputeLobes(int32_t aRadius, int32_t aLobes[3][2])
{
int32_t major, minor, final;
/* See http://www.w3.org/TR/SVG/filters.html#feGaussianBlur for
* some notes about approximating the Gaussian blur with box-blurs.
* The comments below are in the terminology of that page.
*/
int32_t z = aRadius / 3;
switch (aRadius % 3) {
case 0:
// aRadius = z*3; choose d = 2*z + 1
major = minor = final = z;
break;
case 1:
// aRadius = z*3 + 1
// This is a tricky case since there is no value of d which will
// yield a radius of exactly aRadius. If d is odd, i.e. d=2*k + 1
// for some integer k, then the radius will be 3*k. If d is even,
// i.e. d=2*k, then the radius will be 3*k - 1.
// So we have to choose values that don't match the standard
// algorithm.
major = z + 1;
minor = final = z;
break;
case 2:
// aRadius = z*3 + 2; choose d = 2*z + 2
major = final = z + 1;
minor = z;
break;
default:
// Mathematical impossibility!
MOZ_ASSERT(false);
major = minor = final = 0;
}
MOZ_ASSERT(major + minor + final == aRadius);
aLobes[0][0] = major;
aLobes[0][1] = minor;
aLobes[1][0] = minor;
aLobes[1][1] = major;
aLobes[2][0] = final;
aLobes[2][1] = final;
}
static void
SpreadHorizontal(unsigned char* aInput,
unsigned char* aOutput,
int32_t aRadius,
int32_t aWidth,
int32_t aRows,
int32_t aStride,
const IntRect& aSkipRect)
{
if (aRadius == 0) {
memcpy(aOutput, aInput, aStride * aRows);
return;
}
bool skipRectCoversWholeRow = 0 >= aSkipRect.x &&
aWidth <= aSkipRect.XMost();
for (int32_t y = 0; y < aRows; y++) {
// Check whether the skip rect intersects this row. If the skip
// rect covers the whole surface in this row, we can avoid
// this row entirely (and any others along the skip rect).
bool inSkipRectY = y >= aSkipRect.y &&
y < aSkipRect.YMost();
if (inSkipRectY && skipRectCoversWholeRow) {
y = aSkipRect.YMost() - 1;
continue;
}
for (int32_t x = 0; x < aWidth; x++) {
// Check whether we are within the skip rect. If so, go
// to the next point outside the skip rect.
if (inSkipRectY && x >= aSkipRect.x &&
x < aSkipRect.XMost()) {
x = aSkipRect.XMost();
if (x >= aWidth)
break;
}
int32_t sMin = max(x - aRadius, 0);
int32_t sMax = min(x + aRadius, aWidth - 1);
int32_t v = 0;
for (int32_t s = sMin; s <= sMax; ++s) {
v = max<int32_t>(v, aInput[aStride * y + s]);
}
aOutput[aStride * y + x] = v;
}
}
}
static void
SpreadVertical(unsigned char* aInput,
unsigned char* aOutput,
int32_t aRadius,
int32_t aWidth,
int32_t aRows,
int32_t aStride,
const IntRect& aSkipRect)
{
if (aRadius == 0) {
memcpy(aOutput, aInput, aStride * aRows);
return;
}
bool skipRectCoversWholeColumn = 0 >= aSkipRect.y &&
aRows <= aSkipRect.YMost();
for (int32_t x = 0; x < aWidth; x++) {
bool inSkipRectX = x >= aSkipRect.x &&
x < aSkipRect.XMost();
if (inSkipRectX && skipRectCoversWholeColumn) {
x = aSkipRect.XMost() - 1;
continue;
}
for (int32_t y = 0; y < aRows; y++) {
// Check whether we are within the skip rect. If so, go
// to the next point outside the skip rect.
if (inSkipRectX && y >= aSkipRect.y &&
y < aSkipRect.YMost()) {
y = aSkipRect.YMost();
if (y >= aRows)
break;
}
int32_t sMin = max(y - aRadius, 0);
int32_t sMax = min(y + aRadius, aRows - 1);
int32_t v = 0;
for (int32_t s = sMin; s <= sMax; ++s) {
v = max<int32_t>(v, aInput[aStride * s + x]);
}
aOutput[aStride * y + x] = v;
}
}
}
static CheckedInt<int32_t>
RoundUpToMultipleOf4(int32_t aVal)
{
CheckedInt<int32_t> val(aVal);
val += 3;
val /= 4;
val *= 4;
return val;
}
AlphaBoxBlur::AlphaBoxBlur(const Rect& aRect,
const IntSize& aSpreadRadius,
const IntSize& aBlurRadius,
const Rect* aDirtyRect,
const Rect* aSkipRect)
: mSpreadRadius(aSpreadRadius),
mBlurRadius(aBlurRadius),
mData(NULL)
{
Rect rect(aRect);
rect.Inflate(Size(aBlurRadius + aSpreadRadius));
rect.RoundOut();
if (aDirtyRect) {
// If we get passed a dirty rect from layout, we can minimize the
// shadow size and make painting faster.
mHasDirtyRect = true;
mDirtyRect = *aDirtyRect;
Rect requiredBlurArea = mDirtyRect.Intersect(rect);
requiredBlurArea.Inflate(Size(aBlurRadius + aSpreadRadius));
rect = requiredBlurArea.Intersect(rect);
} else {
mHasDirtyRect = false;
}
if (rect.IsEmpty()) {
return;
}
if (aSkipRect) {
// If we get passed a skip rect, we can lower the amount of
// blurring/spreading we need to do. We convert it to IntRect to avoid
// expensive int<->float conversions if we were to use Rect instead.
Rect skipRect = *aSkipRect;
skipRect.RoundIn();
skipRect.Deflate(Size(aBlurRadius + aSpreadRadius));
mSkipRect = IntRect(skipRect.x, skipRect.y, skipRect.width, skipRect.height);
IntRect shadowIntRect(rect.x, rect.y, rect.width, rect.height);
mSkipRect.IntersectRect(mSkipRect, shadowIntRect);
if (mSkipRect.IsEqualInterior(shadowIntRect))
return;
mSkipRect -= shadowIntRect.TopLeft();
} else {
mSkipRect = IntRect(0, 0, 0, 0);
}
mRect = IntRect(rect.x, rect.y, rect.width, rect.height);
CheckedInt<int32_t> stride = RoundUpToMultipleOf4(mRect.width);
if (stride.valid()) {
mStride = stride.value();
CheckedInt<int32_t> size = CheckedInt<int32_t>(mStride) * mRect.height *
sizeof(unsigned char);
if (size.valid()) {
mData = static_cast<unsigned char*>(malloc(size.value()));
memset(mData, 0, size.value());
}
}
}
AlphaBoxBlur::~AlphaBoxBlur()
{
free(mData);
}
unsigned char*
AlphaBoxBlur::GetData()
{
return mData;
}
IntSize
AlphaBoxBlur::GetSize()
{
IntSize size(mRect.width, mRect.height);
return size;
}
int32_t
AlphaBoxBlur::GetStride()
{
return mStride;
}
IntRect
AlphaBoxBlur::GetRect()
{
return mRect;
}
Rect*
AlphaBoxBlur::GetDirtyRect()
{
if (mHasDirtyRect) {
return &mDirtyRect;
}
return NULL;
}
void
AlphaBoxBlur::Blur()
{
if (!mData) {
return;
}
// no need to do all this if not blurring or spreading
if (mBlurRadius != IntSize(0,0) || mSpreadRadius != IntSize(0,0)) {
int32_t stride = GetStride();
// No need to use CheckedInt here - we have validated it in the constructor.
size_t szB = stride * GetSize().height * sizeof(unsigned char);
unsigned char* tmpData = static_cast<unsigned char*>(malloc(szB));
if (!tmpData)
return; // OOM
memset(tmpData, 0, szB);
if (mSpreadRadius.width > 0 || mSpreadRadius.height > 0) {
SpreadHorizontal(mData, tmpData, mSpreadRadius.width, GetSize().width, GetSize().height, stride, mSkipRect);
SpreadVertical(tmpData, mData, mSpreadRadius.height, GetSize().width, GetSize().height, stride, mSkipRect);
}
if (mBlurRadius.width > 0) {
int32_t lobes[3][2];
ComputeLobes(mBlurRadius.width, lobes);
BoxBlurHorizontal(mData, tmpData, lobes[0][0], lobes[0][1], stride, GetSize().height, mSkipRect);
BoxBlurHorizontal(tmpData, mData, lobes[1][0], lobes[1][1], stride, GetSize().height, mSkipRect);
BoxBlurHorizontal(mData, tmpData, lobes[2][0], lobes[2][1], stride, GetSize().height, mSkipRect);
} else {
memcpy(tmpData, mData, stride * GetSize().height);
}
if (mBlurRadius.height > 0) {
int32_t lobes[3][2];
ComputeLobes(mBlurRadius.height, lobes);
BoxBlurVertical(tmpData, mData, lobes[0][0], lobes[0][1], stride, GetSize().height, mSkipRect);
BoxBlurVertical(mData, tmpData, lobes[1][0], lobes[1][1], stride, GetSize().height, mSkipRect);
BoxBlurVertical(tmpData, mData, lobes[2][0], lobes[2][1], stride, GetSize().height, mSkipRect);
} else {
memcpy(mData, tmpData, stride * GetSize().height);
}
free(tmpData);
}
}
/**
* Compute the box blur size (which we're calling the blur radius) from
* the standard deviation.
*
* Much of this, the 3 * sqrt(2 * pi) / 4, is the known value for
* approximating a Gaussian using box blurs. This yields quite a good
* approximation for a Gaussian. Then we multiply this by 1.5 since our
* code wants the radius of the entire triple-box-blur kernel instead of
* the diameter of an individual box blur. For more details, see:
* http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement
* https://bugzilla.mozilla.org/show_bug.cgi?id=590039#c19
*/
static const Float GAUSSIAN_SCALE_FACTOR = (3 * sqrt(2 * M_PI) / 4) * 1.5;
IntSize
AlphaBoxBlur::CalculateBlurRadius(const Point& aStd)
{
IntSize size(static_cast<int32_t>(floor(aStd.x * GAUSSIAN_SCALE_FACTOR + 0.5)),
static_cast<int32_t>(floor(aStd.y * GAUSSIAN_SCALE_FACTOR + 0.5)));
return size;
}
}
}
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