1/*
2 * Copyright 2011 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "include/effects/SkBlurImageFilter.h"
9
10#include <algorithm>
11
12#include "include/core/SkBitmap.h"
13#include "include/core/SkTileMode.h"
14#include "include/private/SkColorData.h"
15#include "include/private/SkNx.h"
16#include "include/private/SkTFitsIn.h"
17#include "src/core/SkArenaAlloc.h"
18#include "src/core/SkAutoPixmapStorage.h"
19#include "src/core/SkGpuBlurUtils.h"
20#include "src/core/SkImageFilter_Base.h"
21#include "src/core/SkOpts.h"
22#include "src/core/SkReadBuffer.h"
23#include "src/core/SkSpecialImage.h"
24#include "src/core/SkWriteBuffer.h"
25
26#if SK_SUPPORT_GPU
27#include "include/gpu/GrContext.h"
28#include "src/gpu/GrTextureProxy.h"
29#include "src/gpu/SkGr.h"
30#endif
31
32namespace {
33
34class SkBlurImageFilterImpl final : public SkImageFilter_Base {
35public:
36 SkBlurImageFilterImpl(SkScalar sigmaX, SkScalar sigmaY, SkTileMode tileMode,
37 sk_sp<SkImageFilter> input, const CropRect* cropRect)
38 : INHERITED(&input, 1, cropRect)
39 , fSigma{sigmaX, sigmaY}
40 , fTileMode(tileMode) {}
41
42 SkRect computeFastBounds(const SkRect&) const override;
43
44protected:
45 void flatten(SkWriteBuffer&) const override;
46 sk_sp<SkSpecialImage> onFilterImage(const Context&, SkIPoint* offset) const override;
47 SkIRect onFilterNodeBounds(const SkIRect& src, const SkMatrix& ctm,
48 MapDirection, const SkIRect* inputRect) const override;
49
50private:
51 friend void SkBlurImageFilter::RegisterFlattenables();
52 SK_FLATTENABLE_HOOKS(SkBlurImageFilterImpl)
53
54#if SK_SUPPORT_GPU
55 sk_sp<SkSpecialImage> gpuFilter(
56 const Context& ctx, SkVector sigma,
57 const sk_sp<SkSpecialImage> &input,
58 SkIRect inputBounds, SkIRect dstBounds, SkIPoint inputOffset, SkIPoint* offset) const;
59#endif
60
61 SkSize fSigma;
62 SkTileMode fTileMode;
63
64 typedef SkImageFilter_Base INHERITED;
65};
66
67} // end namespace
68
69static SkTileMode to_sktilemode(SkBlurImageFilter::TileMode tileMode) {
70 switch(tileMode) {
71 case SkBlurImageFilter::kClamp_TileMode:
72 return SkTileMode::kClamp;
73 case SkBlurImageFilter::kRepeat_TileMode:
74 return SkTileMode::kRepeat;
75 case SkBlurImageFilter::kClampToBlack_TileMode:
76 // Fall through
77 default:
78 return SkTileMode::kDecal;
79 }
80}
81
82sk_sp<SkImageFilter> SkBlurImageFilter::Make(SkScalar sigmaX, SkScalar sigmaY,
83 sk_sp<SkImageFilter> input,
84 const SkImageFilter::CropRect* cropRect,
85 TileMode tileMode) {
86 return Make(sigmaX, sigmaY, to_sktilemode(tileMode), std::move(input), cropRect);
87}
88
89sk_sp<SkImageFilter> SkBlurImageFilter::Make(SkScalar sigmaX, SkScalar sigmaY, SkTileMode tileMode,
90 sk_sp<SkImageFilter> input,
91 const SkImageFilter::CropRect* cropRect) {
92 if (sigmaX < SK_ScalarNearlyZero && sigmaY < SK_ScalarNearlyZero && !cropRect) {
93 return input;
94 }
95 return sk_sp<SkImageFilter>(
96 new SkBlurImageFilterImpl(sigmaX, sigmaY, tileMode, input, cropRect));
97}
98
99void SkBlurImageFilter::RegisterFlattenables() { SK_REGISTER_FLATTENABLE(SkBlurImageFilterImpl); }
100
101///////////////////////////////////////////////////////////////////////////////
102
103sk_sp<SkFlattenable> SkBlurImageFilterImpl::CreateProc(SkReadBuffer& buffer) {
104 SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 1);
105 SkScalar sigmaX = buffer.readScalar();
106 SkScalar sigmaY = buffer.readScalar();
107 SkTileMode tileMode;
108 if (buffer.isVersionLT(SkPicturePriv::kTileModeInBlurImageFilter_Version)) {
109 tileMode = SkTileMode::kDecal;
110 } else if (buffer.isVersionLT(SkPicturePriv::kCleanupImageFilterEnums_Version)) {
111 tileMode = to_sktilemode(buffer.read32LE(SkBlurImageFilter::kLast_TileMode));
112 } else {
113 tileMode = buffer.read32LE(SkTileMode::kLastTileMode);
114 }
115
116 static_assert(SkBlurImageFilter::kLast_TileMode == 2, "CreateProc");
117
118 return SkBlurImageFilter::Make(
119 sigmaX, sigmaY, tileMode, common.getInput(0), &common.cropRect());
120}
121
122void SkBlurImageFilterImpl::flatten(SkWriteBuffer& buffer) const {
123 this->INHERITED::flatten(buffer);
124 buffer.writeScalar(fSigma.fWidth);
125 buffer.writeScalar(fSigma.fHeight);
126
127 // Fuzzer sanity checks
128 static_assert((int) SkTileMode::kLastTileMode == 3 && SkBlurImageFilter::kLast_TileMode == 2,
129 "SkBlurImageFilterImpl::flatten");
130 SkASSERT(fTileMode <= SkTileMode::kLastTileMode);
131 buffer.writeInt(static_cast<int>(fTileMode));
132}
133
134// This is defined by the SVG spec:
135// https://drafts.fxtf.org/filter-effects/#feGaussianBlurElement
136static int calculate_window(double sigma) {
137 // NB 136 is the largest sigma that will not cause a buffer full of 255 mask values to overflow
138 // using the Gauss filter. It also limits the size of buffers used hold intermediate values.
139 // Explanation of maximums:
140 // sum0 = window * 255
141 // sum1 = window * sum0 -> window * window * 255
142 // sum2 = window * sum1 -> window * window * window * 255 -> window^3 * 255
143 //
144 // The value window^3 * 255 must fit in a uint32_t. So,
145 // window^3 < 2^32. window = 255.
146 //
147 // window = floor(sigma * 3 * sqrt(2 * kPi) / 4 + 0.5)
148 // For window <= 255, the largest value for sigma is 136.
149 sigma = SkTPin(sigma, 0.0, 136.0);
150 auto possibleWindow = static_cast<int>(floor(sigma * 3 * sqrt(2 * SK_DoublePI) / 4 + 0.5));
151 return std::max(1, possibleWindow);
152}
153
154// Calculating the border is tricky. The border is the distance in pixels between the first dst
155// pixel and the first src pixel (or the last src pixel and the last dst pixel).
156// I will go through the odd case which is simpler, and then through the even case. Given a
157// stack of filters seven wide for the odd case of three passes.
158//
159// S
160// aaaAaaa
161// bbbBbbb
162// cccCccc
163// D
164//
165// The furthest changed pixel is when the filters are in the following configuration.
166//
167// S
168// aaaAaaa
169// bbbBbbb
170// cccCccc
171// D
172//
173// The A pixel is calculated using the value S, the B uses A, and the C uses B, and
174// finally D is C. So, with a window size of seven the border is nine. In the odd case, the
175// border is 3*((window - 1)/2).
176//
177// For even cases the filter stack is more complicated. The spec specifies two passes
178// of even filters and a final pass of odd filters. A stack for a width of six looks like
179// this.
180//
181// S
182// aaaAaa
183// bbBbbb
184// cccCccc
185// D
186//
187// The furthest pixel looks like this.
188//
189// S
190// aaaAaa
191// bbBbbb
192// cccCccc
193// D
194//
195// For a window of six, the border value is eight. In the even case the border is 3 *
196// (window/2) - 1.
197static int calculate_border(int window) {
198 return (window & 1) == 1 ? 3 * ((window - 1) / 2) : 3 * (window / 2) - 1;
199}
200
201static int calculate_buffer(int window) {
202 int bufferSize = window - 1;
203 return (window & 1) == 1 ? 3 * bufferSize : 3 * bufferSize + 1;
204}
205
206// blur_one_direction implements the common three pass box filter approximation of Gaussian blur,
207// but combines all three passes into a single pass. This approach is facilitated by three circular
208// buffers the width of the window which track values for trailing edges of each of the three
209// passes. This allows the algorithm to use more precision in the calculation because the values
210// are not rounded each pass. And this implementation also avoids a trap that's easy to fall
211// into resulting in blending in too many zeroes near the edge.
212//
213// In general, a window sum has the form:
214// sum_n+1 = sum_n + leading_edge - trailing_edge.
215// If instead we do the subtraction at the end of the previous iteration, we can just
216// calculate the sums instead of having to do the subtractions too.
217//
218// In previous iteration:
219// sum_n+1 = sum_n - trailing_edge.
220//
221// In this iteration:
222// sum_n+1 = sum_n + leading_edge.
223//
224// Now we can stack all three sums and do them at once. Sum0 gets its leading edge from the
225// actual data. Sum1's leading edge is just Sum0, and Sum2's leading edge is Sum1. So, doing the
226// three passes at the same time has the form:
227//
228// sum0_n+1 = sum0_n + leading edge
229// sum1_n+1 = sum1_n + sum0_n+1
230// sum2_n+1 = sum2_n + sum1_n+1
231//
232// sum2_n+1 / window^3 is the new value of the destination pixel.
233//
234// Reduce the sums by the trailing edges which were stored in the circular buffers,
235// for the next go around. This is the case for odd sized windows, even windows the the third
236// circular buffer is one larger then the first two circular buffers.
237//
238// sum2_n+2 = sum2_n+1 - buffer2[i];
239// buffer2[i] = sum1;
240// sum1_n+2 = sum1_n+1 - buffer1[i];
241// buffer1[i] = sum0;
242// sum0_n+2 = sum0_n+1 - buffer0[i];
243// buffer0[i] = leading edge
244//
245// This is all encapsulated in the processValue function below.
246//
247using Pass0And1 = Sk4u[2];
248// The would be dLeft parameter is assumed to be 0.
249static void blur_one_direction(Sk4u* buffer, int window,
250 int srcLeft, int srcRight, int dstRight,
251 const uint32_t* src, int srcXStride, int srcYStride, int srcH,
252 uint32_t* dst, int dstXStride, int dstYStride) {
253
254 // The circular buffers are one less than the window.
255 auto pass0Count = window - 1,
256 pass1Count = window - 1,
257 pass2Count = (window & 1) == 1 ? window - 1 : window;
258
259 Pass0And1* buffer01Start = (Pass0And1*)buffer;
260 Sk4u* buffer2Start = buffer + pass0Count + pass1Count;
261 Pass0And1* buffer01End = (Pass0And1*)buffer2Start;
262 Sk4u* buffer2End = buffer2Start + pass2Count;
263
264 // If the window is odd then the divisor is just window ^ 3 otherwise,
265 // it is window * window * (window + 1) = window ^ 3 + window ^ 2;
266 auto window2 = window * window;
267 auto window3 = window2 * window;
268 auto divisor = (window & 1) == 1 ? window3 : window3 + window2;
269
270 // NB the sums in the blur code use the following technique to avoid
271 // adding 1/2 to round the divide.
272 //
273 // Sum/d + 1/2 == (Sum + h) / d
274 // Sum + d(1/2) == Sum + h
275 // h == (1/2)d
276 //
277 // But the d/2 it self should be rounded.
278 // h == d/2 + 1/2 == (d + 1) / 2
279 //
280 // weight = 1 / d * 2 ^ 32
281 auto weight = static_cast<uint32_t>(round(1.0 / divisor * (1ull << 32)));
282 auto half = static_cast<uint32_t>((divisor + 1) / 2);
283
284 auto border = calculate_border(window);
285
286 // Calculate the start and end of the source pixels with respect to the destination start.
287 auto srcStart = srcLeft - border,
288 srcEnd = srcRight - border,
289 dstEnd = dstRight;
290
291 for (auto y = 0; y < srcH; y++) {
292 auto buffer01Cursor = buffer01Start;
293 auto buffer2Cursor = buffer2Start;
294
295 Sk4u sum0{0u};
296 Sk4u sum1{0u};
297 Sk4u sum2{half};
298
299 sk_bzero(buffer01Start, (buffer2End - (Sk4u *) (buffer01Start)) * sizeof(*buffer2Start));
300
301 // Given an expanded input pixel, move the window ahead using the leadingEdge value.
302 auto processValue = [&](const Sk4u& leadingEdge) -> Sk4u {
303 sum0 += leadingEdge;
304 sum1 += sum0;
305 sum2 += sum1;
306
307 Sk4u value = sum2.mulHi(weight);
308
309 sum2 -= *buffer2Cursor;
310 *buffer2Cursor = sum1;
311 buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : buffer2Start;
312
313 sum1 -= (*buffer01Cursor)[1];
314 (*buffer01Cursor)[1] = sum0;
315 sum0 -= (*buffer01Cursor)[0];
316 (*buffer01Cursor)[0] = leadingEdge;
317 buffer01Cursor =
318 (buffer01Cursor + 1) < buffer01End ? buffer01Cursor + 1 : buffer01Start;
319
320 return value;
321 };
322
323 auto srcIdx = srcStart;
324 auto dstIdx = 0;
325 const uint32_t* srcCursor = src;
326 uint32_t* dstCursor = dst;
327
328 // The destination pixels are not effected by the src pixels,
329 // change to zero as per the spec.
330 // https://drafts.fxtf.org/filter-effects/#FilterPrimitivesOverviewIntro
331 while (dstIdx < srcIdx) {
332 *dstCursor = 0;
333 dstCursor += dstXStride;
334 SK_PREFETCH(dstCursor);
335 dstIdx++;
336 }
337
338 // The edge of the source is before the edge of the destination. Calculate the sums for
339 // the pixels before the start of the destination.
340 while (dstIdx > srcIdx) {
341 Sk4u leadingEdge = srcIdx < srcEnd ? SkNx_cast<uint32_t>(Sk4b::Load(srcCursor)) : 0;
342 (void) processValue(leadingEdge);
343 srcCursor += srcXStride;
344 srcIdx++;
345 }
346
347 // The dstIdx and srcIdx are in sync now; the code just uses the dstIdx for both now.
348 // Consume the source generating pixels to dst.
349 auto loopEnd = std::min(dstEnd, srcEnd);
350 while (dstIdx < loopEnd) {
351 Sk4u leadingEdge = SkNx_cast<uint32_t>(Sk4b::Load(srcCursor));
352 SkNx_cast<uint8_t>(processValue(leadingEdge)).store(dstCursor);
353 srcCursor += srcXStride;
354 dstCursor += dstXStride;
355 SK_PREFETCH(dstCursor);
356 dstIdx++;
357 }
358
359 // The leading edge is beyond the end of the source. Assume that the pixels
360 // are now 0x0000 until the end of the destination.
361 loopEnd = dstEnd;
362 while (dstIdx < loopEnd) {
363 SkNx_cast<uint8_t>(processValue(0u)).store(dstCursor);
364 dstCursor += dstXStride;
365 SK_PREFETCH(dstCursor);
366 dstIdx++;
367 }
368
369 src += srcYStride;
370 dst += dstYStride;
371 }
372}
373
374static sk_sp<SkSpecialImage> copy_image_with_bounds(
375 const SkImageFilter_Base::Context& ctx, const sk_sp<SkSpecialImage> &input,
376 SkIRect srcBounds, SkIRect dstBounds) {
377 SkBitmap inputBM;
378 if (!input->getROPixels(&inputBM)) {
379 return nullptr;
380 }
381
382 if (inputBM.colorType() != kN32_SkColorType) {
383 return nullptr;
384 }
385
386 SkBitmap src;
387 inputBM.extractSubset(&src, srcBounds);
388
389 // Make everything relative to the destination bounds.
390 srcBounds.offset(-dstBounds.x(), -dstBounds.y());
391 dstBounds.offset(-dstBounds.x(), -dstBounds.y());
392
393 auto srcW = srcBounds.width(),
394 dstW = dstBounds.width(),
395 dstH = dstBounds.height();
396
397 SkImageInfo dstInfo = SkImageInfo::Make(dstW, dstH, inputBM.colorType(), inputBM.alphaType());
398
399 SkBitmap dst;
400 if (!dst.tryAllocPixels(dstInfo)) {
401 return nullptr;
402 }
403
404 // There is no blurring to do, but we still need to copy the source while accounting for the
405 // dstBounds. Remember that the src was intersected with the dst.
406 int y = 0;
407 size_t dstWBytes = dstW * sizeof(uint32_t);
408 for (;y < srcBounds.top(); y++) {
409 sk_bzero(dst.getAddr32(0, y), dstWBytes);
410 }
411
412 for (;y < srcBounds.bottom(); y++) {
413 int x = 0;
414 uint32_t* dstPtr = dst.getAddr32(0, y);
415 for (;x < srcBounds.left(); x++) {
416 *dstPtr++ = 0;
417 }
418
419 memcpy(dstPtr, src.getAddr32(x - srcBounds.left(), y - srcBounds.top()),
420 srcW * sizeof(uint32_t));
421
422 dstPtr += srcW;
423 x += srcW;
424
425 for (;x < dstBounds.right(); x++) {
426 *dstPtr++ = 0;
427 }
428 }
429
430 for (;y < dstBounds.bottom(); y++) {
431 sk_bzero(dst.getAddr32(0, y), dstWBytes);
432 }
433
434 return SkSpecialImage::MakeFromRaster(SkIRect::MakeWH(dstBounds.width(),
435 dstBounds.height()),
436 dst, ctx.surfaceProps());
437}
438
439// TODO: Implement CPU backend for different fTileMode.
440static sk_sp<SkSpecialImage> cpu_blur(
441 const SkImageFilter_Base::Context& ctx,
442 SkVector sigma, const sk_sp<SkSpecialImage> &input,
443 SkIRect srcBounds, SkIRect dstBounds) {
444 auto windowW = calculate_window(sigma.x()),
445 windowH = calculate_window(sigma.y());
446
447 if (windowW <= 1 && windowH <= 1) {
448 return copy_image_with_bounds(ctx, input, srcBounds, dstBounds);
449 }
450
451 SkBitmap inputBM;
452
453 if (!input->getROPixels(&inputBM)) {
454 return nullptr;
455 }
456
457 if (inputBM.colorType() != kN32_SkColorType) {
458 return nullptr;
459 }
460
461 SkBitmap src;
462 inputBM.extractSubset(&src, srcBounds);
463
464 // Make everything relative to the destination bounds.
465 srcBounds.offset(-dstBounds.x(), -dstBounds.y());
466 dstBounds.offset(-dstBounds.x(), -dstBounds.y());
467
468 auto srcW = srcBounds.width(),
469 srcH = srcBounds.height(),
470 dstW = dstBounds.width(),
471 dstH = dstBounds.height();
472
473 SkImageInfo dstInfo = inputBM.info().makeWH(dstW, dstH);
474
475 SkBitmap dst;
476 if (!dst.tryAllocPixels(dstInfo)) {
477 return nullptr;
478 }
479
480 auto bufferSizeW = calculate_buffer(windowW),
481 bufferSizeH = calculate_buffer(windowH);
482
483 // The amount 1024 is enough for buffers up to 10 sigma. The tmp bitmap will be
484 // allocated on the heap.
485 SkSTArenaAlloc<1024> alloc;
486 Sk4u* buffer = alloc.makeArrayDefault<Sk4u>(std::max(bufferSizeW, bufferSizeH));
487
488 // Basic Plan: The three cases to handle
489 // * Horizontal and Vertical - blur horizontally while copying values from the source to
490 // the destination. Then, do an in-place vertical blur.
491 // * Horizontal only - blur horizontally copying values from the source to the destination.
492 // * Vertical only - blur vertically copying values from the source to the destination.
493
494 // Default to vertical only blur case. If a horizontal blur is needed, then these values
495 // will be adjusted while doing the horizontal blur.
496 auto intermediateSrc = static_cast<uint32_t *>(src.getPixels());
497 auto intermediateRowBytesAsPixels = src.rowBytesAsPixels();
498 auto intermediateWidth = srcW;
499
500 // Because the border is calculated before the fork of the GPU/CPU path. The border is
501 // the maximum of the two rendering methods. In the case where sigma is zero, then the
502 // src and dst left values are the same. If sigma is small resulting in a window size of
503 // 1, then border calculations add some pixels which will always be zero. Inset the
504 // destination by those zero pixels. This case is very rare.
505 auto intermediateDst = dst.getAddr32(srcBounds.left(), 0);
506
507 // The following code is executed very rarely, I have never seen it in a real web
508 // page. If sigma is small but not zero then shared GPU/CPU border calculation
509 // code adds extra pixels for the border. Just clear everything to clear those pixels.
510 // This solution is overkill, but very simple.
511 if (windowW == 1 || windowH == 1) {
512 dst.eraseColor(0);
513 }
514
515 if (windowW > 1) {
516 // Make int64 to avoid overflow in multiplication below.
517 int64_t shift = srcBounds.top() - dstBounds.top();
518
519 // For the horizontal blur, starts part way down in anticipation of the vertical blur.
520 // For a vertical sigma of zero shift should be zero. But, for small sigma,
521 // shift may be > 0 but the vertical window could be 1.
522 intermediateSrc = static_cast<uint32_t *>(dst.getPixels())
523 + (shift > 0 ? shift * dst.rowBytesAsPixels() : 0);
524 intermediateRowBytesAsPixels = dst.rowBytesAsPixels();
525 intermediateWidth = dstW;
526 intermediateDst = static_cast<uint32_t *>(dst.getPixels());
527
528 blur_one_direction(
529 buffer, windowW,
530 srcBounds.left(), srcBounds.right(), dstBounds.right(),
531 static_cast<uint32_t *>(src.getPixels()), 1, src.rowBytesAsPixels(), srcH,
532 intermediateSrc, 1, intermediateRowBytesAsPixels);
533 }
534
535 if (windowH > 1) {
536 blur_one_direction(
537 buffer, windowH,
538 srcBounds.top(), srcBounds.bottom(), dstBounds.bottom(),
539 intermediateSrc, intermediateRowBytesAsPixels, 1, intermediateWidth,
540 intermediateDst, dst.rowBytesAsPixels(), 1);
541 }
542
543 return SkSpecialImage::MakeFromRaster(SkIRect::MakeWH(dstBounds.width(),
544 dstBounds.height()),
545 dst, ctx.surfaceProps());
546}
547
548// This rather arbitrary-looking value results in a maximum box blur kernel size
549// of 1000 pixels on the raster path, which matches the WebKit and Firefox
550// implementations. Since the GPU path does not compute a box blur, putting
551// the limit on sigma ensures consistent behaviour between the GPU and
552// raster paths.
553#define MAX_SIGMA SkIntToScalar(532)
554
555static SkVector map_sigma(const SkSize& localSigma, const SkMatrix& ctm) {
556 SkVector sigma = SkVector::Make(localSigma.width(), localSigma.height());
557 ctm.mapVectors(&sigma, 1);
558 sigma.fX = std::min(SkScalarAbs(sigma.fX), MAX_SIGMA);
559 sigma.fY = std::min(SkScalarAbs(sigma.fY), MAX_SIGMA);
560 return sigma;
561}
562
563sk_sp<SkSpecialImage> SkBlurImageFilterImpl::onFilterImage(const Context& ctx,
564 SkIPoint* offset) const {
565 SkIPoint inputOffset = SkIPoint::Make(0, 0);
566
567 sk_sp<SkSpecialImage> input(this->filterInput(0, ctx, &inputOffset));
568 if (!input) {
569 return nullptr;
570 }
571
572 SkIRect inputBounds = SkIRect::MakeXYWH(inputOffset.fX, inputOffset.fY,
573 input->width(), input->height());
574
575 // Calculate the destination bounds.
576 SkIRect dstBounds;
577 if (!this->applyCropRect(this->mapContext(ctx), inputBounds, &dstBounds)) {
578 return nullptr;
579 }
580 if (!inputBounds.intersect(dstBounds)) {
581 return nullptr;
582 }
583
584 // Save the offset in preparation to make all rectangles relative to the inputOffset.
585 SkIPoint resultOffset = SkIPoint::Make(dstBounds.fLeft, dstBounds.fTop);
586
587 // Make all bounds relative to the inputOffset.
588 inputBounds.offset(-inputOffset);
589 dstBounds.offset(-inputOffset);
590
591 SkVector sigma = map_sigma(fSigma, ctx.ctm());
592 if (sigma.x() < 0 || sigma.y() < 0) {
593 return nullptr;
594 }
595
596 sk_sp<SkSpecialImage> result;
597#if SK_SUPPORT_GPU
598 if (ctx.gpuBacked()) {
599 // Ensure the input is in the destination's gamut. This saves us from having to do the
600 // xform during the filter itself.
601 input = ImageToColorSpace(input.get(), ctx.colorType(), ctx.colorSpace());
602 result = this->gpuFilter(ctx, sigma, input, inputBounds, dstBounds, inputOffset,
603 &resultOffset);
604 } else
605#endif
606 {
607 // NB 135 is the largest sigma that will not cause a buffer full of 255 mask values to overflow
608 // using the Gauss filter. It also limits the size of buffers used hold intermediate values. The
609 // additional + 1 added to window represents adding one more leading element before subtracting the
610 // trailing element.
611 // Explanation of maximums:
612 // sum0 = (window + 1) * 255
613 // sum1 = (window + 1) * sum0 -> (window + 1) * (window + 1) * 255
614 // sum2 = (window + 1) * sum1 -> (window + 1) * (window + 1) * (window + 1) * 255 -> window^3 * 255
615 //
616 // The value (window + 1)^3 * 255 must fit in a uint32_t. So,
617 // (window + 1)^3 * 255 < 2^32. window = 255.
618 //
619 // window = floor(sigma * 3 * sqrt(2 * kPi) / 4)
620 // For window <= 255, the largest value for sigma is 135.
621 sigma.fX = SkTPin(sigma.fX, 0.0f, 135.0f);
622 sigma.fY = SkTPin(sigma.fY, 0.0f, 135.0f);
623
624 result = cpu_blur(ctx, sigma, input, inputBounds, dstBounds);
625 }
626
627 // Return the resultOffset if the blur succeeded.
628 if (result != nullptr) {
629 *offset = resultOffset;
630 }
631 return result;
632}
633
634#if SK_SUPPORT_GPU
635sk_sp<SkSpecialImage> SkBlurImageFilterImpl::gpuFilter(
636 const Context& ctx, SkVector sigma, const sk_sp<SkSpecialImage> &input, SkIRect inputBounds,
637 SkIRect dstBounds, SkIPoint inputOffset, SkIPoint* offset) const {
638 if (0 == sigma.x() && 0 == sigma.y()) {
639 offset->fX = inputBounds.x() + inputOffset.fX;
640 offset->fY = inputBounds.y() + inputOffset.fY;
641 return input->makeSubset(inputBounds);
642 }
643
644 auto context = ctx.getContext();
645
646 GrSurfaceProxyView inputView = input->view(context);
647 if (!inputView.proxy()) {
648 return nullptr;
649 }
650 SkASSERT(inputView.asTextureProxy());
651
652 // TODO (michaelludwig) - The color space choice is odd, should it just be ctx.refColorSpace()?
653 dstBounds.offset(input->subset().topLeft());
654 inputBounds.offset(input->subset().topLeft());
655 auto renderTargetContext = SkGpuBlurUtils::GaussianBlur(
656 context,
657 std::move(inputView),
658 SkColorTypeToGrColorType(input->colorType()),
659 input->alphaType(),
660 ctx.colorSpace() ? sk_ref_sp(input->getColorSpace()) : nullptr,
661 dstBounds,
662 inputBounds,
663 sigma.x(),
664 sigma.y(),
665 fTileMode);
666 if (!renderTargetContext) {
667 return nullptr;
668 }
669
670 return SkSpecialImage::MakeDeferredFromGpu(context,
671 SkIRect::MakeSize(dstBounds.size()),
672 kNeedNewImageUniqueID_SpecialImage,
673 renderTargetContext->readSurfaceView(),
674 renderTargetContext->colorInfo().colorType(),
675 sk_ref_sp(input->getColorSpace()),
676 ctx.surfaceProps());
677}
678#endif
679
680SkRect SkBlurImageFilterImpl::computeFastBounds(const SkRect& src) const {
681 SkRect bounds = this->getInput(0) ? this->getInput(0)->computeFastBounds(src) : src;
682 bounds.outset(fSigma.width() * 3, fSigma.height() * 3);
683 return bounds;
684}
685
686SkIRect SkBlurImageFilterImpl::onFilterNodeBounds(const SkIRect& src, const SkMatrix& ctm,
687 MapDirection, const SkIRect* inputRect) const {
688 SkVector sigma = map_sigma(fSigma, ctm);
689 return src.makeOutset(SkScalarCeilToInt(sigma.x() * 3), SkScalarCeilToInt(sigma.y() * 3));
690}
691