1 /*
2 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.java2d.marlin;
27
28 import jdk.internal.misc.Unsafe;
29
30 /**
31 * An object used to cache pre-rendered complex paths.
32 *
33 * @see Renderer
34 */
35 public final class MarlinCache implements MarlinConst {
36
37 static final boolean FORCE_RLE = MarlinProperties.isForceRLE();
38 static final boolean FORCE_NO_RLE = MarlinProperties.isForceNoRLE();
39 // minimum width to try using RLE encoding:
40 static final int RLE_MIN_WIDTH
41 = Math.max(BLOCK_SIZE, MarlinProperties.getRLEMinWidth());
42 // maximum width for RLE encoding:
43 // values are stored as int [x|alpha] where alpha is 8 bits
44 static final int RLE_MAX_WIDTH = 1 << (24 - 1);
45
46 // 2048 (pixelSize) alpha values (width) x 32 rows (tile) = 64K bytes
47 // x1 instead of 4 bytes (RLE) ie 1/4 capacity or average good RLE compression
48 static final long INITIAL_CHUNK_ARRAY = TILE_SIZE * INITIAL_PIXEL_DIM; // 64K
49
50 // The alpha map used by this object (taken out of our map cache) to convert
51 // pixel coverage counts gotten from MarlinCache (which are in the range
52 // [0, maxalpha]) into alpha values, which are in [0,256).
53 static final byte[] ALPHA_MAP;
54
55 static final OffHeapArray ALPHA_MAP_UNSAFE;
56
57 static {
58 final byte[] _ALPHA_MAP = buildAlphaMap(MAX_AA_ALPHA);
59
60 ALPHA_MAP_UNSAFE = new OffHeapArray(_ALPHA_MAP, _ALPHA_MAP.length); // 1K
61 ALPHA_MAP =_ALPHA_MAP;
62
63 final Unsafe _unsafe = OffHeapArray.unsafe;
64 final long addr = ALPHA_MAP_UNSAFE.address;
65
66 for (int i = 0; i < _ALPHA_MAP.length; i++) {
67 _unsafe.putByte(addr + i, _ALPHA_MAP[i]);
68 }
69 }
70
71 int bboxX0, bboxY0, bboxX1, bboxY1;
72
73 // 1D dirty arrays
74 // row index in rowAAChunk[]
75 final long[] rowAAChunkIndex = new long[TILE_SIZE];
76 // first pixel (inclusive) for each row
77 final int[] rowAAx0 = new int[TILE_SIZE];
78 // last pixel (exclusive) for each row
79 final int[] rowAAx1 = new int[TILE_SIZE];
80 // encoding mode (0=raw, 1=RLE encoding) for each row
81 final int[] rowAAEnc = new int[TILE_SIZE];
82 // coded length (RLE encoding) for each row
83 final long[] rowAALen = new long[TILE_SIZE];
84 // last position in RLE decoding for each row (getAlpha):
85 final long[] rowAAPos = new long[TILE_SIZE];
86
87 // dirty off-heap array containing pixel coverages for (32) rows (packed)
88 // if encoding=raw, it contains alpha coverage values (val) as integer
89 // if encoding=RLE, it contains tuples (val, last x-coordinate exclusive)
90 // use rowAAx0/rowAAx1 to get row indices within this chunk
91 final OffHeapArray rowAAChunk;
92
93 // current position in rowAAChunk array
94 long rowAAChunkPos;
95
96 // touchedTile[i] is the sum of all the alphas in the tile with
97 // x=j*TILE_SIZE+bboxX0.
98 int[] touchedTile;
99
100 // per-thread renderer context
101 final RendererContext rdrCtx;
102
103 // large cached touchedTile (dirty)
104 final int[] touchedTile_initial = new int[INITIAL_ARRAY]; // 1 tile line
105
106 int tileMin, tileMax;
107
108 boolean useRLE = false;
109
110 MarlinCache(final RendererContext rdrCtx) {
111 this.rdrCtx = rdrCtx;
112
113 rowAAChunk = new OffHeapArray(rdrCtx, INITIAL_CHUNK_ARRAY);
114
115 touchedTile = touchedTile_initial;
116
117 // tile used marks:
118 tileMin = Integer.MAX_VALUE;
119 tileMax = Integer.MIN_VALUE;
120 }
121
122 void init(int minx, int miny, int maxx, int maxy, int edgeSumDeltaY)
123 {
124 // assert maxy >= miny && maxx >= minx;
125 bboxX0 = minx;
126 bboxY0 = miny;
127 bboxX1 = maxx;
128 bboxY1 = maxy;
129
130 final int width = (maxx - minx);
131
132 if (FORCE_NO_RLE) {
133 useRLE = false;
134 } else if (FORCE_RLE) {
135 useRLE = true;
136 } else {
137 // heuristics: use both bbox area and complexity
138 // ie number of primitives:
139
140 // fast check min and max width (maxx < 23bits):
141 if (width <= RLE_MIN_WIDTH || width >= RLE_MAX_WIDTH) {
142 useRLE = false;
143 } else {
144 // perimeter approach: how fit the total length into given height:
145
146 // if stroking: meanCrossings /= 2 => divide edgeSumDeltaY by 2
147 final int heightSubPixel
148 = (((maxy - miny) << SUBPIXEL_LG_POSITIONS_Y) << rdrCtx.stroking);
149
150 // check meanDist > block size:
151 // check width / (meanCrossings - 1) >= RLE_THRESHOLD
152
153 // fast case: (meanCrossingPerPixel <= 2) means 1 span only
154 useRLE = (edgeSumDeltaY <= (heightSubPixel << 1))
155 // note: already checked (meanCrossingPerPixel <= 2)
156 // rewritten to avoid division:
157 || (width * heightSubPixel) >
158 ((edgeSumDeltaY - heightSubPixel) << BLOCK_SIZE_LG);
159 // ((edgeSumDeltaY - heightSubPixel) * RLE_THRESHOLD);
160 // ((edgeSumDeltaY - heightSubPixel) << BLOCK_TH_LG);
161
162 if (doTrace && !useRLE) {
163 final float meanCrossings
164 = ((float) edgeSumDeltaY) / heightSubPixel;
165 final float meanDist = width / (meanCrossings - 1);
166
167 System.out.println("High complexity: "
168 + " for bbox[width = " + width
169 + " height = " + (maxy - miny)
170 + "] edgeSumDeltaY = " + edgeSumDeltaY
171 + " heightSubPixel = " + heightSubPixel
172 + " meanCrossings = "+ meanCrossings
173 + " meanDist = " + meanDist
174 + " width = " + (width * heightSubPixel)
175 + " <= criteria: " + ((edgeSumDeltaY - heightSubPixel) << BLOCK_SIZE_LG)
176 );
177 }
178 }
179 }
180
181 // the ceiling of (maxy - miny + 1) / TILE_SIZE;
182 final int nxTiles = (width + TILE_SIZE) >> TILE_SIZE_LG;
183
184 if (nxTiles > INITIAL_ARRAY) {
185 if (doStats) {
186 RendererContext.stats.stat_array_marlincache_touchedTile
187 .add(nxTiles);
188 }
189 touchedTile = rdrCtx.getIntArray(nxTiles);
190 }
191 }
192
193 /**
194 * Disposes this cache:
195 * clean up before reusing this instance
196 */
197 void dispose() {
198 // Reset touchedTile if needed:
199 resetTileLine(0);
200
201 // Return arrays:
202 if (touchedTile != touchedTile_initial) {
203 rdrCtx.putIntArray(touchedTile, 0, 0); // already zero filled
204 touchedTile = touchedTile_initial;
205 }
206 // At last: resize back off-heap rowAA to initial size
207 if (rowAAChunk.length != INITIAL_CHUNK_ARRAY) {
208 // note: may throw OOME:
209 rowAAChunk.resize(INITIAL_CHUNK_ARRAY);
210 }
211 if (doCleanDirty) {
212 // Force zero-fill dirty arrays:
213 rowAAChunk.fill(BYTE_0);
214 }
215 }
216
217 void resetTileLine(final int pminY) {
218 // update bboxY0 to process a complete tile line [0 - 32]
219 bboxY0 = pminY;
220
221 // reset current pos
222 if (doStats) {
223 RendererContext.stats.stat_cache_rowAAChunk.add(rowAAChunkPos);
224 }
225 rowAAChunkPos = 0L;
226
227 // Reset touchedTile:
228 if (tileMin != Integer.MAX_VALUE) {
229 if (doStats) {
230 RendererContext.stats.stat_cache_tiles.add(tileMax - tileMin);
231 }
232 // clean only dirty touchedTile:
233 if (tileMax == 1) {
234 touchedTile[0] = 0;
235 } else {
236 IntArrayCache.fill(touchedTile, tileMin, tileMax, 0);
237 }
238 // reset tile used marks:
239 tileMin = Integer.MAX_VALUE;
240 tileMax = Integer.MIN_VALUE;
241 }
242
243 if (doCleanDirty) {
244 // Force zero-fill dirty arrays:
245 rowAAChunk.fill(BYTE_0);
246 }
247 }
248
249 void clearAARow(final int y) {
250 // process tile line [0 - 32]
251 final int row = y - bboxY0;
252
253 // update pixel range:
254 rowAAx0[row] = 0; // first pixel inclusive
255 rowAAx1[row] = 0; // last pixel exclusive
256 rowAAEnc[row] = 0; // raw encoding
257
258 // note: leave rowAAChunkIndex[row] undefined
259 // and rowAALen[row] & rowAAPos[row] (RLE)
260 }
261
262 /**
263 * Copy the given alpha data into the rowAA cache
264 * @param alphaRow alpha data to copy from
265 * @param y y pixel coordinate
266 * @param px0 first pixel inclusive x0
267 * @param px1 last pixel exclusive x1
268 */
269 void copyAARowNoRLE(final int[] alphaRow, final int y,
270 final int px0, final int px1)
271 {
272 if (doMonitors) {
273 RendererContext.stats.mon_rdr_copyAARow.start();
274 }
275
276 // skip useless pixels above boundary
277 final int px_bbox1 = FloatMath.min(px1, bboxX1);
278
279 if (doLogBounds) {
280 MarlinUtils.logInfo("row = [" + px0 + " ... " + px_bbox1
281 + " (" + px1 + ") [ for y=" + y);
282 }
283
284 final int row = y - bboxY0;
285
286 // update pixel range:
287 rowAAx0[row] = px0; // first pixel inclusive
288 rowAAx1[row] = px_bbox1; // last pixel exclusive
289 rowAAEnc[row] = 0; // raw encoding
290
291 // get current position (bytes):
292 final long pos = rowAAChunkPos;
293 // update row index to current position:
294 rowAAChunkIndex[row] = pos;
295
296 // determine need array size (may overflow):
297 final long needSize = pos + (px_bbox1 - px0);
298
299 // update next position (bytes):
300 rowAAChunkPos = needSize;
301
302 // update row data:
303 final OffHeapArray _rowAAChunk = rowAAChunk;
304 // ensure rowAAChunk capacity:
305 if (_rowAAChunk.length < needSize) {
306 expandRowAAChunk(needSize);
307 }
308 if (doStats) {
309 RendererContext.stats.stat_cache_rowAA.add(px_bbox1 - px0);
310 }
311
312 // rowAA contains only alpha values for range[x0; x1[
313 final int[] _touchedTile = touchedTile;
314 final int _TILE_SIZE_LG = TILE_SIZE_LG;
315
316 final int from = px0 - bboxX0; // first pixel inclusive
317 final int to = px_bbox1 - bboxX0; // last pixel exclusive
318
319 final Unsafe _unsafe = OffHeapArray.unsafe;
320 final long SIZE_BYTE = 1L;
321 final long addr_alpha = ALPHA_MAP_UNSAFE.address;
322 long addr_off = _rowAAChunk.address + pos;
323
324 // compute alpha sum into rowAA:
325 for (int x = from, val = 0; x < to; x++) {
326 // alphaRow is in [0; MAX_COVERAGE]
327 val += alphaRow[x]; // [from; to[
328
329 // ensure values are in [0; MAX_AA_ALPHA] range
330 if (DO_AA_RANGE_CHECK) {
331 if (val < 0) {
332 System.out.println("Invalid coverage = " + val);
333 val = 0;
334 }
335 if (val > MAX_AA_ALPHA) {
336 System.out.println("Invalid coverage = " + val);
337 val = MAX_AA_ALPHA;
338 }
339 }
340
341 // store alpha sum (as byte):
342 if (val == 0) {
343 _unsafe.putByte(addr_off, (byte)0); // [0..255]
344 } else {
345 _unsafe.putByte(addr_off, _unsafe.getByte(addr_alpha + val)); // [0..255]
346
347 // update touchedTile
348 _touchedTile[x >> _TILE_SIZE_LG] += val;
349 }
350 addr_off += SIZE_BYTE;
351 }
352
353 // update tile used marks:
354 int tx = from >> _TILE_SIZE_LG; // inclusive
355 if (tx < tileMin) {
356 tileMin = tx;
357 }
358
359 tx = ((to - 1) >> _TILE_SIZE_LG) + 1; // exclusive (+1 to be sure)
360 if (tx > tileMax) {
361 tileMax = tx;
362 }
363
364 if (doLogBounds) {
365 MarlinUtils.logInfo("clear = [" + from + " ... " + to + "[");
366 }
367
368 // Clear alpha row for reuse:
369 IntArrayCache.fill(alphaRow, from, px1 - bboxX0, 0);
370
371 if (doMonitors) {
372 RendererContext.stats.mon_rdr_copyAARow.stop();
373 }
374 }
375
376 void copyAARowRLE_WithBlockFlags(final int[] blkFlags, final int[] alphaRow,
377 final int y, final int px0, final int px1)
378 {
379 if (doMonitors) {
380 RendererContext.stats.mon_rdr_copyAARow.start();
381 }
382
383 // Copy rowAA data into the piscesCache if one is present
384 final int _bboxX0 = bboxX0;
385
386 // process tile line [0 - 32]
387 final int row = y - bboxY0;
388 final int from = px0 - _bboxX0; // first pixel inclusive
389
390 // skip useless pixels above boundary
391 final int px_bbox1 = FloatMath.min(px1, bboxX1);
392 final int to = px_bbox1 - _bboxX0; // last pixel exclusive
393
394 if (doLogBounds) {
395 MarlinUtils.logInfo("row = [" + px0 + " ... " + px_bbox1
396 + " (" + px1 + ") [ for y=" + y);
397 }
398
399 // get current position:
400 final long initialPos = startRLERow(row, px0, px_bbox1);
401
402 // determine need array size:
403 // pessimistic: max needed size = deltaX x 4 (1 int)
404 final int maxLen = (to - from);
405 final long needSize = initialPos + (maxLen << 2);
406
407 // update row data:
408 OffHeapArray _rowAAChunk = rowAAChunk;
409 // ensure rowAAChunk capacity:
410 if (_rowAAChunk.length < needSize) {
411 expandRowAAChunk(needSize);
412 }
413
414 final Unsafe _unsafe = OffHeapArray.unsafe;
415 final long SIZE_INT = 4L;
416 final long addr_alpha = ALPHA_MAP_UNSAFE.address;
417 long addr_off = _rowAAChunk.address + initialPos;
418
419 final int[] _touchedTile = touchedTile;
420 final int _TILE_SIZE_LG = TILE_SIZE_LG;
421 final int _BLK_SIZE_LG = BLOCK_SIZE_LG;
422
423 // traverse flagged blocks:
424 final int blkW = (from >> _BLK_SIZE_LG);
425 final int blkE = (to >> _BLK_SIZE_LG) + 1;
426
427 // Perform run-length encoding and store results in the piscesCache
428 int val = 0;
429 int cx0 = from;
430 int runLen;
431
432 final int _MAX_VALUE = Integer.MAX_VALUE;
433 int last_t0 = _MAX_VALUE;
434
435 int skip = 0;
436
437 for (int t = blkW, blk_x0, blk_x1, cx, delta; t <= blkE; t++) {
438 if (blkFlags[t] != 0) {
439 blkFlags[t] = 0;
440
441 if (last_t0 == _MAX_VALUE) {
442 last_t0 = t;
443 }
444 continue;
445 }
446 if (last_t0 != _MAX_VALUE) {
447 // emit blocks:
448 blk_x0 = FloatMath.max(last_t0 << _BLK_SIZE_LG, from);
449 last_t0 = _MAX_VALUE;
450
451 // (last block pixel+1) inclusive => +1
452 blk_x1 = FloatMath.min((t << _BLK_SIZE_LG) + 1, to);
453
454 for (cx = blk_x0; cx < blk_x1; cx++) {
455 if ((delta = alphaRow[cx]) != 0) {
456 alphaRow[cx] = 0;
457
458 // not first rle entry:
459 if (cx != cx0) {
460 runLen = cx - cx0;
461
462 // store alpha coverage (ensure within bounds):
463 // as [absX|val] where:
464 // absX is the absolute x-coordinate:
465 // note: last pixel exclusive (>= 0)
466 // note: it should check X is smaller than 23bits (overflow)!
467
468 // special case to encode entries into a single int:
469 if (val == 0) {
470 _unsafe.putInt(addr_off,
471 ((_bboxX0 + cx) << 8)
472 );
473 } else {
474 _unsafe.putInt(addr_off,
475 ((_bboxX0 + cx) << 8)
476 | (((int) _unsafe.getByte(addr_alpha + val)) & 0xFF) // [0..255]
477 );
478
479 if (runLen == 1) {
480 _touchedTile[cx0 >> _TILE_SIZE_LG] += val;
481 } else {
482 touchTile(cx0, val, cx, runLen, _touchedTile);
483 }
484 }
485 addr_off += SIZE_INT;
486
487 if (doStats) {
488 RendererContext.stats.hist_tile_generator_encoding_runLen
489 .add(runLen);
490 }
491 cx0 = cx;
492 }
493
494 // alpha value = running sum of coverage delta:
495 val += delta;
496
497 // ensure values are in [0; MAX_AA_ALPHA] range
498 if (DO_AA_RANGE_CHECK) {
499 if (val < 0) {
500 System.out.println("Invalid coverage = " + val);
501 val = 0;
502 }
503 if (val > MAX_AA_ALPHA) {
504 System.out.println("Invalid coverage = " + val);
505 val = MAX_AA_ALPHA;
506 }
507 }
508 }
509 }
510 } else if (doStats) {
511 skip++;
512 }
513 }
514
515 // Process remaining RLE run:
516 runLen = to - cx0;
517
518 // store alpha coverage (ensure within bounds):
519 // as (int)[absX|val] where:
520 // absX is the absolute x-coordinate in bits 31 to 8 and val in bits 0..7
521 // note: last pixel exclusive (>= 0)
522 // note: it should check X is smaller than 23bits (overflow)!
523
524 // special case to encode entries into a single int:
525 if (val == 0) {
526 _unsafe.putInt(addr_off,
527 ((_bboxX0 + to) << 8)
528 );
529 } else {
530 _unsafe.putInt(addr_off,
531 ((_bboxX0 + to) << 8)
532 | (((int) _unsafe.getByte(addr_alpha + val)) & 0xFF) // [0..255]
533 );
534
535 if (runLen == 1) {
536 _touchedTile[cx0 >> _TILE_SIZE_LG] += val;
537 } else {
538 touchTile(cx0, val, to, runLen, _touchedTile);
539 }
540 }
541 addr_off += SIZE_INT;
542
543 if (doStats) {
544 RendererContext.stats.hist_tile_generator_encoding_runLen
545 .add(runLen);
546 }
547
548 long len = (addr_off - _rowAAChunk.address);
549
550 // update coded length as bytes:
551 rowAALen[row] = (len - initialPos);
552
553 // update current position:
554 rowAAChunkPos = len;
555
556 if (doStats) {
557 RendererContext.stats.stat_cache_rowAA.add(rowAALen[row]);
558 RendererContext.stats.hist_tile_generator_encoding_ratio.add(
559 (100 * skip) / (blkE - blkW)
560 );
561 }
562
563 // update tile used marks:
564 int tx = from >> _TILE_SIZE_LG; // inclusive
565 if (tx < tileMin) {
566 tileMin = tx;
567 }
568
569 tx = ((to - 1) >> _TILE_SIZE_LG) + 1; // exclusive (+1 to be sure)
570 if (tx > tileMax) {
571 tileMax = tx;
572 }
573
574 // Clear alpha row for reuse:
575 if (px1 > bboxX1) {
576 alphaRow[to ] = 0;
577 alphaRow[to + 1] = 0;
578 }
579 if (doChecks) {
580 IntArrayCache.check(blkFlags, 0, blkFlags.length, 0);
581 IntArrayCache.check(alphaRow, 0, alphaRow.length, 0);
582 }
583
584 if (doMonitors) {
585 RendererContext.stats.mon_rdr_copyAARow.stop();
586 }
587 }
588
589 long startRLERow(final int row, final int x0, final int x1) {
590 // rows are supposed to be added by increasing y.
591 rowAAx0[row] = x0; // first pixel inclusive
592 rowAAx1[row] = x1; // last pixel exclusive
593 rowAAEnc[row] = 1; // RLE encoding
594 rowAAPos[row] = 0L; // position = 0
595
596 // update row index to current position:
597 return (rowAAChunkIndex[row] = rowAAChunkPos);
598 }
599
600 private void expandRowAAChunk(final long needSize) {
601 if (doStats) {
602 RendererContext.stats.stat_array_marlincache_rowAAChunk
603 .add(needSize);
604 }
605
606 // note: throw IOOB if neededSize > 2Gb:
607 final long newSize = ArrayCache.getNewLargeSize(rowAAChunk.length, needSize);
608
609 rowAAChunk.resize(newSize);
610 }
611
612 private void touchTile(final int x0, final int val, final int x1,
613 final int runLen,
614 final int[] _touchedTile)
615 {
616 // the x and y of the current row, minus bboxX0, bboxY0
617 // process tile line [0 - 32]
618 final int _TILE_SIZE_LG = TILE_SIZE_LG;
619
620 // update touchedTile
621 int tx = (x0 >> _TILE_SIZE_LG);
622
623 // handle trivial case: same tile (x0, x0+runLen)
624 if (tx == (x1 >> _TILE_SIZE_LG)) {
625 // same tile:
626 _touchedTile[tx] += val * runLen;
627 return;
628 }
629
630 final int tx1 = (x1 - 1) >> _TILE_SIZE_LG;
631
632 if (tx <= tx1) {
633 final int nextTileXCoord = (tx + 1) << _TILE_SIZE_LG;
634 _touchedTile[tx++] += val * (nextTileXCoord - x0);
635 }
636 if (tx < tx1) {
637 // don't go all the way to tx1 - we need to handle the last
638 // tile as a special case (just like we did with the first
639 final int tileVal = (val << _TILE_SIZE_LG);
640 for (; tx < tx1; tx++) {
641 _touchedTile[tx] += tileVal;
642 }
643 }
644 // they will be equal unless x0 >> TILE_SIZE_LG == tx1
645 if (tx == tx1) {
646 final int txXCoord = tx << _TILE_SIZE_LG;
647 final int nextTileXCoord = (tx + 1) << _TILE_SIZE_LG;
648
649 final int lastXCoord = (nextTileXCoord <= x1) ? nextTileXCoord : x1;
650 _touchedTile[tx] += val * (lastXCoord - txXCoord);
651 }
652 }
653
654 int alphaSumInTile(final int x) {
655 return touchedTile[(x - bboxX0) >> TILE_SIZE_LG];
656 }
657
658 @Override
659 public String toString() {
660 return "bbox = ["
661 + bboxX0 + ", " + bboxY0 + " => "
662 + bboxX1 + ", " + bboxY1 + "]\n";
663 }
664
665 private static byte[] buildAlphaMap(final int maxalpha) {
666 // double size !
667 final byte[] alMap = new byte[maxalpha << 1];
668 final int halfmaxalpha = maxalpha >> 2;
669 for (int i = 0; i <= maxalpha; i++) {
670 alMap[i] = (byte) ((i * 255 + halfmaxalpha) / maxalpha);
671 // System.out.println("alphaMap[" + i + "] = "
672 // + Byte.toUnsignedInt(alMap[i]));
673 }
674 return alMap;
675 }
676 }