| /* |
| * 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 SkAntiRun_DEFINED |
| #define SkAntiRun_DEFINED |
| |
| #include "include/private/base/SkTo.h" |
| #include "src/core/SkBlitter.h" |
| |
| /** Sparse array of run-length-encoded alpha (supersampling coverage) values. |
| Sparseness allows us to independently compose several paths into the |
| same SkAlphaRuns buffer. |
| */ |
| |
| class SkAlphaRuns { |
| public: |
| int16_t* fRuns; |
| uint8_t* fAlpha; |
| |
| // Return 0-255 given 0-256 |
| static inline SkAlpha CatchOverflow(int alpha) { |
| SkASSERT(alpha >= 0 && alpha <= 256); |
| return alpha - (alpha >> 8); |
| } |
| |
| /// Returns true if the scanline contains only a single run, |
| /// of alpha value 0. |
| bool empty() const { |
| SkASSERT(fRuns[0] > 0); |
| return fAlpha[0] == 0 && fRuns[fRuns[0]] == 0; |
| } |
| |
| /// Reinitialize for a new scanline. |
| void reset(int width); |
| |
| /** |
| * Insert into the buffer a run starting at (x-offsetX): |
| * if startAlpha > 0 |
| * one pixel with value += startAlpha, |
| * max 255 |
| * if middleCount > 0 |
| * middleCount pixels with value += maxValue |
| * if stopAlpha > 0 |
| * one pixel with value += stopAlpha |
| * Returns the offsetX value that should be passed on the next call, |
| * assuming we're on the same scanline. If the caller is switching |
| * scanlines, then offsetX should be 0 when this is called. |
| */ |
| SK_ALWAYS_INLINE int add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha, |
| U8CPU maxValue, int offsetX) { |
| SkASSERT(middleCount >= 0); |
| SkASSERT(x >= 0 && x + (startAlpha != 0) + middleCount + (stopAlpha != 0) <= fWidth); |
| |
| SkASSERT(fRuns[offsetX] >= 0); |
| |
| int16_t* runs = fRuns + offsetX; |
| uint8_t* alpha = fAlpha + offsetX; |
| uint8_t* lastAlpha = alpha; |
| x -= offsetX; |
| |
| if (startAlpha) { |
| SkAlphaRuns::Break(runs, alpha, x, 1); |
| /* I should be able to just add alpha[x] + startAlpha. |
| However, if the trailing edge of the previous span and the leading |
| edge of the current span round to the same super-sampled x value, |
| I might overflow to 256 with this add, hence the funny subtract (crud). |
| */ |
| unsigned tmp = alpha[x] + startAlpha; |
| SkASSERT(tmp <= 256); |
| alpha[x] = SkToU8(tmp - (tmp >> 8)); // was (tmp >> 7), but that seems wrong if we're trying to catch 256 |
| |
| runs += x + 1; |
| alpha += x + 1; |
| x = 0; |
| SkDEBUGCODE(this->validate();) |
| } |
| |
| if (middleCount) { |
| SkAlphaRuns::Break(runs, alpha, x, middleCount); |
| alpha += x; |
| runs += x; |
| x = 0; |
| do { |
| alpha[0] = SkToU8(CatchOverflow(alpha[0] + maxValue)); |
| int n = runs[0]; |
| SkASSERT(n <= middleCount); |
| alpha += n; |
| runs += n; |
| middleCount -= n; |
| } while (middleCount > 0); |
| SkDEBUGCODE(this->validate();) |
| lastAlpha = alpha; |
| } |
| |
| if (stopAlpha) { |
| SkAlphaRuns::Break(runs, alpha, x, 1); |
| alpha += x; |
| alpha[0] = SkToU8(alpha[0] + stopAlpha); |
| SkDEBUGCODE(this->validate();) |
| lastAlpha = alpha; |
| } |
| |
| return SkToS32(lastAlpha - fAlpha); // new offsetX |
| } |
| |
| SkDEBUGCODE(void assertValid(int y, int maxStep) const;) |
| SkDEBUGCODE(void dump() const;) |
| |
| /** |
| * Break the runs in the buffer at offsets x and x+count, properly |
| * updating the runs to the right and left. |
| * i.e. from the state AAAABBBB, run-length encoded as A4B4, |
| * Break(..., 2, 5) would produce AAAABBBB rle as A2A2B3B1. |
| * Allows add() to sum another run to some of the new sub-runs. |
| * i.e. adding ..CCCCC. would produce AADDEEEB, rle as A2D2E3B1. |
| */ |
| static void Break(int16_t runs[], uint8_t alpha[], int x, int count) { |
| SkASSERT(count > 0 && x >= 0); |
| |
| // SkAlphaRuns::BreakAt(runs, alpha, x); |
| // SkAlphaRuns::BreakAt(&runs[x], &alpha[x], count); |
| |
| int16_t* next_runs = runs + x; |
| uint8_t* next_alpha = alpha + x; |
| |
| while (x > 0) { |
| int n = runs[0]; |
| SkASSERT(n > 0); |
| |
| if (x < n) { |
| alpha[x] = alpha[0]; |
| runs[0] = SkToS16(x); |
| runs[x] = SkToS16(n - x); |
| break; |
| } |
| runs += n; |
| alpha += n; |
| x -= n; |
| } |
| |
| runs = next_runs; |
| alpha = next_alpha; |
| x = count; |
| |
| for (;;) { |
| int n = runs[0]; |
| SkASSERT(n > 0); |
| |
| if (x < n) { |
| alpha[x] = alpha[0]; |
| runs[0] = SkToS16(x); |
| runs[x] = SkToS16(n - x); |
| break; |
| } |
| x -= n; |
| if (x <= 0) { |
| break; |
| } |
| runs += n; |
| alpha += n; |
| } |
| } |
| |
| /** |
| * Cut (at offset x in the buffer) a run into two shorter runs with |
| * matching alpha values. |
| * Used by the RectClipBlitter to trim a RLE encoding to match the |
| * clipping rectangle. |
| */ |
| static void BreakAt(int16_t runs[], uint8_t alpha[], int x) { |
| while (x > 0) { |
| int n = runs[0]; |
| SkASSERT(n > 0); |
| |
| if (x < n) { |
| alpha[x] = alpha[0]; |
| runs[0] = SkToS16(x); |
| runs[x] = SkToS16(n - x); |
| break; |
| } |
| runs += n; |
| alpha += n; |
| x -= n; |
| } |
| } |
| |
| private: |
| SkDEBUGCODE(int fWidth;) |
| SkDEBUGCODE(void validate() const;) |
| }; |
| |
| #endif |