gecko/gfx/thebes/gfxBlur.cpp

492 lines
18 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* ***** 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 gfx thebes code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2008
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Eric Butler <zantifon@gmail.com>
*
* 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 "gfxBlur.h"
#include "nsMathUtils.h"
#include "nsTArray.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
gfxAlphaBoxBlur::gfxAlphaBoxBlur()
{
}
gfxAlphaBoxBlur::~gfxAlphaBoxBlur()
{
}
gfxContext*
gfxAlphaBoxBlur::Init(const gfxRect& aRect,
const gfxIntSize& aSpreadRadius,
const gfxIntSize& aBlurRadius,
const gfxRect* aDirtyRect,
const gfxRect* aSkipRect)
{
mSpreadRadius = aSpreadRadius;
mBlurRadius = aBlurRadius;
gfxRect rect(aRect);
rect.Inflate(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 = PR_TRUE;
mDirtyRect = *aDirtyRect;
gfxRect requiredBlurArea = mDirtyRect.Intersect(rect);
requiredBlurArea.Inflate(aBlurRadius + aSpreadRadius);
rect = requiredBlurArea.Intersect(rect);
} else {
mHasDirtyRect = PR_FALSE;
}
// Check rect empty after accounting for aDirtyRect, since that may have
// make the rectangle empty. BoxBlurVertical and BoxBlurHorizontal require
// that we have a nonzero number of rows and columns.
if (rect.IsEmpty())
return nsnull;
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 nsIntRect to avoid
// expensive int<->float conversions if we were to use gfxRect instead.
gfxRect skipRect = *aSkipRect;
skipRect.RoundIn();
skipRect.Deflate(aBlurRadius + aSpreadRadius);
gfxUtils::GfxRectToIntRect(skipRect, &mSkipRect);
nsIntRect shadowIntRect;
gfxUtils::GfxRectToIntRect(rect, &shadowIntRect);
mSkipRect.IntersectRect(mSkipRect, shadowIntRect);
if (mSkipRect.IsEqualInterior(shadowIntRect))
return nsnull;
mSkipRect -= shadowIntRect.TopLeft();
} else {
mSkipRect = nsIntRect(0, 0, 0, 0);
}
// Make an alpha-only surface to draw on. We will play with the data after
// everything is drawn to create a blur effect.
mImageSurface = new gfxImageSurface(gfxIntSize(static_cast<PRInt32>(rect.Width()), static_cast<PRInt32>(rect.Height())),
gfxASurface::ImageFormatA8);
if (!mImageSurface || mImageSurface->CairoStatus())
return nsnull;
// Use a device offset so callers don't need to worry about translating
// coordinates, they can draw as if this was part of the destination context
// at the coordinates of rect.
mImageSurface->SetDeviceOffset(-rect.TopLeft());
mContext = new gfxContext(mImageSurface);
return mContext;
}
/**
* 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,
PRInt32 aLeftLobe,
PRInt32 aRightLobe,
PRInt32 aWidth,
PRInt32 aRows,
const nsIntRect& aSkipRect)
{
NS_ASSERTION(aWidth > 0, "Can't handle zero width here");
PRInt32 boxSize = aLeftLobe + aRightLobe + 1;
PRBool skipRectCoversWholeRow = 0 >= aSkipRect.x &&
aWidth <= aSkipRect.XMost();
for (PRInt32 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).
PRBool inSkipRectY = y >= aSkipRect.y &&
y < aSkipRect.YMost();
if (inSkipRectY && skipRectCoversWholeRow) {
y = aSkipRect.YMost() - 1;
continue;
}
PRInt32 alphaSum = 0;
for (PRInt32 i = 0; i < boxSize; i++) {
PRInt32 pos = i - aLeftLobe;
// See assertion above; if aWidth is zero, then we would have no
// valid position to clamp to.
pos = NS_MAX(pos, 0);
pos = NS_MIN(pos, aWidth - 1);
alphaSum += aInput[aWidth * y + pos];
}
for (PRInt32 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 (PRInt32 i = 0; i < boxSize; i++) {
PRInt32 pos = x + i - aLeftLobe;
// See assertion above; if aWidth is zero, then we would have no
// valid position to clamp to.
pos = NS_MAX(pos, 0);
pos = NS_MIN(pos, aWidth - 1);
alphaSum += aInput[aWidth * y + pos];
}
}
PRInt32 tmp = x - aLeftLobe;
PRInt32 last = NS_MAX(tmp, 0);
PRInt32 next = NS_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,
PRInt32 aTopLobe,
PRInt32 aBottomLobe,
PRInt32 aWidth,
PRInt32 aRows,
const nsIntRect& aSkipRect)
{
NS_ASSERTION(aRows > 0, "Can't handle zero rows here");
PRInt32 boxSize = aTopLobe + aBottomLobe + 1;
PRBool skipRectCoversWholeColumn = 0 >= aSkipRect.y &&
aRows <= aSkipRect.YMost();
for (PRInt32 x = 0; x < aWidth; x++) {
PRBool inSkipRectX = x >= aSkipRect.x &&
x < aSkipRect.XMost();
if (inSkipRectX && skipRectCoversWholeColumn) {
x = aSkipRect.XMost() - 1;
continue;
}
PRInt32 alphaSum = 0;
for (PRInt32 i = 0; i < boxSize; i++) {
PRInt32 pos = i - aTopLobe;
// See assertion above; if aRows is zero, then we would have no
// valid position to clamp to.
pos = NS_MAX(pos, 0);
pos = NS_MIN(pos, aRows - 1);
alphaSum += aInput[aWidth * pos + x];
}
for (PRInt32 y = 0; y < aRows; y++) {
if (inSkipRectX && y >= aSkipRect.y &&
y < aSkipRect.YMost()) {
y = aSkipRect.YMost();
if (y >= aRows)
break;
alphaSum = 0;
for (PRInt32 i = 0; i < boxSize; i++) {
PRInt32 pos = y + i - aTopLobe;
// See assertion above; if aRows is zero, then we would have no
// valid position to clamp to.
pos = NS_MAX(pos, 0);
pos = NS_MIN(pos, aRows - 1);
alphaSum += aInput[aWidth * pos + x];
}
}
PRInt32 tmp = y - aTopLobe;
PRInt32 last = NS_MAX(tmp, 0);
PRInt32 next = NS_MIN(tmp + boxSize, aRows - 1);
aOutput[aWidth * y + x] = alphaSum/boxSize;
alphaSum += aInput[aWidth * next + x] -
aInput[aWidth * last + x];
}
}
}
static void ComputeLobes(PRInt32 aRadius, PRInt32 aLobes[3][2])
{
PRInt32 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.
*/
PRInt32 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:
NS_ERROR("Mathematical impossibility.");
major = minor = final = 0;
}
NS_ASSERTION(major + minor + final == aRadius,
"Lobes don't sum to the right length");
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,
PRInt32 aRadius,
PRInt32 aWidth,
PRInt32 aRows,
PRInt32 aStride,
const nsIntRect& aSkipRect)
{
if (aRadius == 0) {
memcpy(aOutput, aInput, aStride*aRows);
return;
}
PRBool skipRectCoversWholeRow = 0 >= aSkipRect.x &&
aWidth <= aSkipRect.XMost();
for (PRInt32 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).
PRBool inSkipRectY = y >= aSkipRect.y &&
y < aSkipRect.YMost();
if (inSkipRectY && skipRectCoversWholeRow) {
y = aSkipRect.YMost() - 1;
continue;
}
for (PRInt32 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;
}
PRInt32 sMin = PR_MAX(x - aRadius, 0);
PRInt32 sMax = PR_MIN(x + aRadius, aWidth - 1);
PRInt32 v = 0;
for (PRInt32 s = sMin; s <= sMax; ++s) {
v = PR_MAX(v, aInput[aStride * y + s]);
}
aOutput[aStride * y + x] = v;
}
}
}
static void
SpreadVertical(unsigned char* aInput,
unsigned char* aOutput,
PRInt32 aRadius,
PRInt32 aWidth,
PRInt32 aRows,
PRInt32 aStride,
const nsIntRect& aSkipRect)
{
if (aRadius == 0) {
memcpy(aOutput, aInput, aStride*aRows);
return;
}
PRBool skipRectCoversWholeColumn = 0 >= aSkipRect.y &&
aRows <= aSkipRect.YMost();
for (PRInt32 x = 0; x < aWidth; x++) {
PRBool inSkipRectX = x >= aSkipRect.x &&
x < aSkipRect.XMost();
if (inSkipRectX && skipRectCoversWholeColumn) {
x = aSkipRect.XMost() - 1;
continue;
}
for (PRInt32 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;
}
PRInt32 sMin = PR_MAX(y - aRadius, 0);
PRInt32 sMax = PR_MIN(y + aRadius, aRows - 1);
PRInt32 v = 0;
for (PRInt32 s = sMin; s <= sMax; ++s) {
v = PR_MAX(v, aInput[aStride * s + x]);
}
aOutput[aStride * y + x] = v;
}
}
}
void
gfxAlphaBoxBlur::Paint(gfxContext* aDestinationCtx, const gfxPoint& offset)
{
if (!mContext)
return;
unsigned char* boxData = mImageSurface->Data();
// no need to do all this if not blurring or spreading
if (mBlurRadius != gfxIntSize(0,0) || mSpreadRadius != gfxIntSize(0,0)) {
nsTArray<unsigned char> tempAlphaDataBuf;
PRSize szB = mImageSurface->GetDataSize();
if (!tempAlphaDataBuf.SetLength(szB))
return; // OOM
unsigned char* tmpData = tempAlphaDataBuf.Elements();
// .SetLength above doesn't initialise the new elements since
// they are unsigned chars and so have no default constructor.
// So we have to initialise them by hand.
memset(tmpData, 0, szB);
PRInt32 stride = mImageSurface->Stride();
PRInt32 rows = mImageSurface->Height();
PRInt32 width = mImageSurface->Width();
if (mSpreadRadius.width > 0 || mSpreadRadius.height > 0) {
SpreadHorizontal(boxData, tmpData, mSpreadRadius.width, width, rows, stride, mSkipRect);
SpreadVertical(tmpData, boxData, mSpreadRadius.height, width, rows, stride, mSkipRect);
}
if (mBlurRadius.width > 0) {
PRInt32 lobes[3][2];
ComputeLobes(mBlurRadius.width, lobes);
BoxBlurHorizontal(boxData, tmpData, lobes[0][0], lobes[0][1], stride, rows, mSkipRect);
BoxBlurHorizontal(tmpData, boxData, lobes[1][0], lobes[1][1], stride, rows, mSkipRect);
BoxBlurHorizontal(boxData, tmpData, lobes[2][0], lobes[2][1], stride, rows, mSkipRect);
} else {
memcpy(tmpData, boxData, stride*rows);
}
if (mBlurRadius.height > 0) {
PRInt32 lobes[3][2];
ComputeLobes(mBlurRadius.height, lobes);
BoxBlurVertical(tmpData, boxData, lobes[0][0], lobes[0][1], stride, rows, mSkipRect);
BoxBlurVertical(boxData, tmpData, lobes[1][0], lobes[1][1], stride, rows, mSkipRect);
BoxBlurVertical(tmpData, boxData, lobes[2][0], lobes[2][1], stride, rows, mSkipRect);
} else {
memcpy(boxData, tmpData, stride*rows);
}
}
// Avoid a semi-expensive clip operation if we can, otherwise
// clip to the dirty rect
if (mHasDirtyRect) {
aDestinationCtx->Save();
aDestinationCtx->NewPath();
aDestinationCtx->Rectangle(mDirtyRect);
aDestinationCtx->Clip();
aDestinationCtx->Mask(mImageSurface, offset);
aDestinationCtx->Restore();
} else {
aDestinationCtx->Mask(mImageSurface, offset);
}
}
/**
* 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 gfxFloat GAUSSIAN_SCALE_FACTOR = (3 * sqrt(2 * M_PI) / 4) * 1.5;
gfxIntSize gfxAlphaBoxBlur::CalculateBlurRadius(const gfxPoint& aStd)
{
return gfxIntSize(
static_cast<PRInt32>(floor(aStd.x * GAUSSIAN_SCALE_FACTOR + 0.5)),
static_cast<PRInt32>(floor(aStd.y * GAUSSIAN_SCALE_FACTOR + 0.5)));
}