/*
 * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.java2d.marlin;

import java.util.Arrays;
import sun.java2d.pipe.AATileGenerator;
import jdk.internal.misc.Unsafe;

final class MarlinTileGenerator implements AATileGenerator, MarlinConst {

    private static final boolean DISABLE_BLEND = false;

    private static final int MAX_TILE_ALPHA_SUM = TILE_W * TILE_H * MAX_AA_ALPHA;

    private static final int TH_AA_ALPHA_FILL_EMPTY = ((MAX_AA_ALPHA + 1) / 3); // 33%
    private static final int TH_AA_ALPHA_FILL_FULL  = ((MAX_AA_ALPHA + 1) * 2 / 3); // 66%

    private static final int FILL_TILE_W = TILE_W >> 1; // half tile width

    static {
        if (MAX_TILE_ALPHA_SUM <= 0) {
            throw new IllegalStateException("Invalid MAX_TILE_ALPHA_SUM: " + MAX_TILE_ALPHA_SUM);
        }
        if (DO_TRACE) {
            MarlinUtils.logInfo("MAX_AA_ALPHA           : " + MAX_AA_ALPHA);
            MarlinUtils.logInfo("TH_AA_ALPHA_FILL_EMPTY : " + TH_AA_ALPHA_FILL_EMPTY);
            MarlinUtils.logInfo("TH_AA_ALPHA_FILL_FULL  : " + TH_AA_ALPHA_FILL_FULL);
            MarlinUtils.logInfo("FILL_TILE_W            : " + FILL_TILE_W);
        }
    }

    private final Renderer rdrF;
    private final DRenderer rdrD;
    private final MarlinCache cache;
    private int x, y;

    // per-thread renderer stats
    final RendererStats rdrStats;

    MarlinTileGenerator(final RendererStats stats, final MarlinRenderer r,
                        final MarlinCache cache)
    {
        this.rdrStats = stats;
        if (r instanceof Renderer) {
            this.rdrF = (Renderer)r;
            this.rdrD = null;
        } else {
            this.rdrF = null;
            this.rdrD = (DRenderer)r;
        }
        this.cache = cache;
    }

    MarlinTileGenerator init() {
        this.x = cache.bboxX0;
        this.y = cache.bboxY0;

        return this; // fluent API
    }

    
Disposes this tile generator:
clean up before reusing this instance
/**
     * Disposes this tile generator:
     * clean up before reusing this instance
     */
    @Override
    public void dispose() {
        if (DO_MONITORS) {
            // called from AAShapePipe.renderTiles() (render tiles end):
            rdrStats.mon_pipe_renderTiles.stop();
        }
        // dispose cache:
        cache.dispose();
        // dispose renderer and recycle the RendererContext instance:
        // bimorphic call optimization:
        if (rdrF != null) {
            rdrF.dispose();
        } else if (rdrD != null) {
            rdrD.dispose();
        }
    }

    void getBbox(int[] bbox) {
        bbox[0] = cache.bboxX0;
        bbox[1] = cache.bboxY0;
        bbox[2] = cache.bboxX1;
        bbox[3] = cache.bboxY1;
    }

    
Gets the width of the tiles that the generator batches output into.
Returns:
the width of the standard alpha tile/**
     * Gets the width of the tiles that the generator batches output into.
     * @return the width of the standard alpha tile
     */
    @Override
    public int getTileWidth() {
        if (DO_MONITORS) {
            // called from AAShapePipe.renderTiles() (render tiles start):
            rdrStats.mon_pipe_renderTiles.start();
        }
        return TILE_W;
    }

    
Gets the height of the tiles that the generator batches output into.
Returns:
the height of the standard alpha tile/**
     * Gets the height of the tiles that the generator batches output into.
     * @return the height of the standard alpha tile
     */
    @Override
    public int getTileHeight() {
        return TILE_H;
    }

    
Gets the typical alpha value that will characterize the current
tile.
The answer may be 0x00 to indicate that the current tile has
no coverage in any of its pixels, or it may be 0xff to indicate
that the current tile is completely covered by the path, or any
other value to indicate non-trivial coverage cases.
Returns:
0x00 for no coverage, 0xff for total coverage, or any other
        value for partial coverage of the tile/**
     * Gets the typical alpha value that will characterize the current
     * tile.
     * The answer may be 0x00 to indicate that the current tile has
     * no coverage in any of its pixels, or it may be 0xff to indicate
     * that the current tile is completely covered by the path, or any
     * other value to indicate non-trivial coverage cases.
     * @return 0x00 for no coverage, 0xff for total coverage, or any other
     *         value for partial coverage of the tile
     */
    @Override
    public int getTypicalAlpha() {
        if (DISABLE_BLEND) {
            // always return empty tiles to disable blending operations
            return 0x00;
        }
        int al = cache.alphaSumInTile(x);
        // Note: if we have a filled rectangle that doesn't end on a tile
        // border, we could still return 0xff, even though al!=maxTileAlphaSum
        // This is because if we return 0xff, our users will fill a rectangle
        // starting at x,y that has width = Math.min(TILE_SIZE, bboxX1-x),
        // and height min(TILE_SIZE,bboxY1-y), which is what should happen.
        // However, to support this, we would have to use 2 Math.min's
        // and 2 multiplications per tile, instead of just 2 multiplications
        // to compute maxTileAlphaSum. The savings offered would probably
        // not be worth it, considering how rare this case is.
        // Note: I have not tested this, so in the future if it is determined
        // that it is worth it, it should be implemented. Perhaps this method's
        // interface should be changed to take arguments the width and height
        // of the current tile. This would eliminate the 2 Math.min calls that
        // would be needed here, since our caller needs to compute these 2
        // values anyway.
        final int alpha = (al == 0x00 ? 0x00
                              : (al == MAX_TILE_ALPHA_SUM ? 0xff : 0x80));
        if (DO_STATS) {
            rdrStats.hist_tile_generator_alpha.add(alpha);
        }
        return alpha;
    }

    
Skips the current tile and moves on to the next tile.
Either this method, or the getAlpha() method should be called
once per tile, but not both.
/**
     * Skips the current tile and moves on to the next tile.
     * Either this method, or the getAlpha() method should be called
     * once per tile, but not both.
     */
    @Override
    public void nextTile() {
        if ((x += TILE_W) >= cache.bboxX1) {
            x = cache.bboxX0;
            y += TILE_H;

            if (y < cache.bboxY1) {
                // compute for the tile line
                // [ y; max(y + TILE_SIZE, bboxY1) ]
                // bimorphic call optimization:
                if (rdrF != null) {
                    rdrF.endRendering(y);
                } else if (rdrD != null) {
                    rdrD.endRendering(y);
                }
            }
        }
    }

    
Gets the alpha coverage values for the current tile.
Either this method, or the nextTile() method should be called
once per tile, but not both.
/**
     * Gets the alpha coverage values for the current tile.
     * Either this method, or the nextTile() method should be called
     * once per tile, but not both.
     */
    @Override
    public void getAlpha(final byte[] tile, final int offset,
                                            final int rowstride)
    {
        if (cache.useRLE) {
            getAlphaRLE(tile, offset, rowstride);
        } else {
            getAlphaNoRLE(tile, offset, rowstride);
        }
    }

    
Gets the alpha coverage values for the current tile.
Either this method, or the nextTile() method should be called
once per tile, but not both.
/**
     * Gets the alpha coverage values for the current tile.
     * Either this method, or the nextTile() method should be called
     * once per tile, but not both.
     */
    private void getAlphaNoRLE(final byte[] tile, final int offset,
                               final int rowstride)
    {
        if (DO_MONITORS) {
            rdrStats.mon_ptg_getAlpha.start();
        }

        // local vars for performance:
        final MarlinCache _cache = this.cache;
        final long[] rowAAChunkIndex = _cache.rowAAChunkIndex;
        final int[] rowAAx0 = _cache.rowAAx0;
        final int[] rowAAx1 = _cache.rowAAx1;

        final int x0 = this.x;
        final int x1 = FloatMath.min(x0 + TILE_W, _cache.bboxX1);

        // note: process tile line [0 - 32[
        final int y0 = 0;
        final int y1 = FloatMath.min(this.y + TILE_H, _cache.bboxY1) - this.y;

        if (DO_LOG_BOUNDS) {
            MarlinUtils.logInfo("getAlpha = [" + x0 + " ... " + x1
                                + "[ [" + y0 + " ... " + y1 + "[");
        }

        final Unsafe _unsafe = OffHeapArray.UNSAFE;
        final long SIZE = 1L;
        final long addr_rowAA = _cache.rowAAChunk.address;
        long addr;

        final int skipRowPixels = (rowstride - (x1 - x0));

        int aax0, aax1, end;
        int idx = offset;

        for (int cy = y0, cx; cy < y1; cy++) {
            // empty line (default)
            cx = x0;

            aax1 = rowAAx1[cy]; // exclusive

            // quick check if there is AA data
            // corresponding to this tile [x0; x1[
            if (aax1 > x0) {
                aax0 = rowAAx0[cy]; // inclusive

                if (aax0 < x1) {
                    // note: cx is the cursor pointer in the tile array
                    // (left to right)
                    cx = aax0;

                    // ensure cx >= x0
                    if (cx <= x0) {
                        cx = x0;
                    } else {
                        // fill line start until first AA pixel rowAA exclusive:
                        for (end = x0; end < cx; end++) {
                            tile[idx++] = 0;
                        }
                    }

                    // now: cx >= x0 and cx >= aax0

                    // Copy AA data (sum alpha data):
                    addr = addr_rowAA + rowAAChunkIndex[cy] + (cx - aax0);

                    for (end = (aax1 <= x1) ? aax1 : x1; cx < end; cx++) {
                        // cx inside tile[x0; x1[ :
                        tile[idx++] = _unsafe.getByte(addr); // [0-255]
                        addr += SIZE;
                    }
                }
            }

            // fill line end
            while (cx < x1) {
                tile[idx++] = 0;
                cx++;
            }

            if (DO_TRACE) {
                for (int i = idx - (x1 - x0); i < idx; i++) {
                    System.out.print(hex(tile[i], 2));
                }
                System.out.println();
            }

            idx += skipRowPixels;
        }

        nextTile();

        if (DO_MONITORS) {
            rdrStats.mon_ptg_getAlpha.stop();
        }
    }

    
Gets the alpha coverage values for the current tile.
Either this method, or the nextTile() method should be called
once per tile, but not both.
/**
     * Gets the alpha coverage values for the current tile.
     * Either this method, or the nextTile() method should be called
     * once per tile, but not both.
     */
    private void getAlphaRLE(final byte[] tile, final int offset,
                             final int rowstride)
    {
        if (DO_MONITORS) {
            rdrStats.mon_ptg_getAlpha.start();
        }

        // Decode run-length encoded alpha mask data
        // The data for row j begins at cache.rowOffsetsRLE[j]
        // and is encoded as a set of 2-byte pairs (val, runLen)
        // terminated by a (0, 0) pair.

        // local vars for performance:
        final MarlinCache _cache = this.cache;
        final long[] rowAAChunkIndex = _cache.rowAAChunkIndex;
        final int[] rowAAx0 = _cache.rowAAx0;
        final int[] rowAAx1 = _cache.rowAAx1;
        final int[] rowAAEnc = _cache.rowAAEnc;
        final long[] rowAALen = _cache.rowAALen;
        final long[] rowAAPos = _cache.rowAAPos;

        final int x0 = this.x;
        final int x1 = FloatMath.min(x0 + TILE_W, _cache.bboxX1);
        final int w  = x1 - x0;

        // note: process tile line [0 - 32[
        final int y0 = 0;
        final int y1 = FloatMath.min(this.y + TILE_H, _cache.bboxY1) - this.y;

        if (DO_LOG_BOUNDS) {
            MarlinUtils.logInfo("getAlpha = [" + x0 + " ... " + x1
                                + "[ [" + y0 + " ... " + y1 + "[");
        }

        // avoid too small area: fill is not faster !
        final int clearTile;
        final byte refVal;
        final int area;

        if ((w >= FILL_TILE_W) && (area = w * y1) > 64) { // 64 / 4 ie 16 words min (faster)
            final int alphaSum = cache.alphaSumInTile(x0);

            if (alphaSum < area * TH_AA_ALPHA_FILL_EMPTY) {
                clearTile = 1;
                refVal = 0;
            } else if (alphaSum > area * TH_AA_ALPHA_FILL_FULL) {
                clearTile = 2;
                refVal = (byte)0xff;
            } else {
                clearTile = 0;
                refVal = 0;
            }
        } else {
            clearTile = 0;
            refVal = 0;
        }

        final Unsafe _unsafe = OffHeapArray.UNSAFE;
        final long SIZE_BYTE = 1L;
        final long SIZE_INT = 4L;
        final long addr_rowAA = _cache.rowAAChunk.address;
        long addr, addr_row, last_addr, addr_end;

        final int skipRowPixels = (rowstride - w);

        int cx, cy, cx1;
        int rx0, rx1, runLen, end;
        int packed;
        byte val;
        int idx = offset;

        switch (clearTile) {
        case 1: // 0x00
            // Clear full tile rows:
            Arrays.fill(tile, offset, offset + (y1 * rowstride), refVal);

            for (cy = y0; cy < y1; cy++) {
                // empty line (default)
                cx = x0;

                if (rowAAEnc[cy] == 0) {
                    // Raw encoding:

                    final int aax1 = rowAAx1[cy]; // exclusive

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (aax1 > x0) {
                        final int aax0 = rowAAx0[cy]; // inclusive

                        if (aax0 < x1) {
                            // note: cx is the cursor pointer in the tile array
                            // (left to right)
                            cx = aax0;

                            // ensure cx >= x0
                            if (cx <= x0) {
                                cx = x0;
                            } else {
                                // skip line start until first AA pixel rowAA exclusive:
                                idx += (cx - x0); // > 0
                            }

                            // now: cx >= x0 and cx >= aax0

                            // Copy AA data (sum alpha data):
                            addr = addr_rowAA + rowAAChunkIndex[cy] + (cx - aax0);

                            for (end = (aax1 <= x1) ? aax1 : x1; cx < end; cx++) {
                                tile[idx++] = _unsafe.getByte(addr); // [0-255]
                                addr += SIZE_BYTE;
                            }
                        }
                    }
                } else {
                    // RLE encoding:

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (rowAAx1[cy] > x0) { // last pixel exclusive

                        cx = rowAAx0[cy]; // inclusive
                        if (cx > x1) {
                            cx = x1;
                        }

                        // skip line start until first AA pixel rowAA exclusive:
                        if (cx > x0) {
                            idx += (cx - x0); // > 0
                        }

                        // get row address:
                        addr_row = addr_rowAA + rowAAChunkIndex[cy];
                        // get row end address:
                        addr_end = addr_row + rowAALen[cy]; // coded length

                        // reuse previous iteration position:
                        addr = addr_row + rowAAPos[cy];

                        last_addr = 0L;

                        while ((cx < x1) && (addr < addr_end)) {
                            // keep current position:
                            last_addr = addr;

                            // packed value:
                            packed = _unsafe.getInt(addr);

                            // last exclusive pixel x-coordinate:
                            cx1 = (packed >> 8);
                            // as bytes:
                            addr += SIZE_INT;

                            rx0 = cx;
                            if (rx0 < x0) {
                                rx0 = x0;
                            }
                            rx1 = cx = cx1;
                            if (rx1 > x1) {
                                rx1 = x1;
                                cx  = x1; // fix last x
                            }
                            // adjust runLen:
                            runLen = rx1 - rx0;

                            // ensure rx1 > rx0:
                            if (runLen > 0) {
                                packed &= 0xFF; // [0-255]

                                if (packed == 0)
                                {
                                    idx += runLen;
                                    continue;
                                }
                                val = (byte) packed; // [0-255]
                                do {
                                    tile[idx++] = val;
                                } while (--runLen > 0);
                            }
                        }

                        // Update last position in RLE entries:
                        if (last_addr != 0L) {
                            // Fix x0:
                            rowAAx0[cy]  = cx; // inclusive
                            // Fix position:
                            rowAAPos[cy] = (last_addr - addr_row);
                        }
                    }
                }

                // skip line end
                if (cx < x1) {
                    idx += (x1 - cx); // > 0
                }

                if (DO_TRACE) {
                    for (int i = idx - (x1 - x0); i < idx; i++) {
                        System.out.print(hex(tile[i], 2));
                    }
                    System.out.println();
                }

                idx += skipRowPixels;
            }
        break;

        case 0:
        default:
            for (cy = y0; cy < y1; cy++) {
                // empty line (default)
                cx = x0;

                if (rowAAEnc[cy] == 0) {
                    // Raw encoding:

                    final int aax1 = rowAAx1[cy]; // exclusive

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (aax1 > x0) {
                        final int aax0 = rowAAx0[cy]; // inclusive

                        if (aax0 < x1) {
                            // note: cx is the cursor pointer in the tile array
                            // (left to right)
                            cx = aax0;

                            // ensure cx >= x0
                            if (cx <= x0) {
                                cx = x0;
                            } else {
                                for (end = x0; end < cx; end++) {
                                    tile[idx++] = 0;
                                }
                            }

                            // now: cx >= x0 and cx >= aax0

                            // Copy AA data (sum alpha data):
                            addr = addr_rowAA + rowAAChunkIndex[cy] + (cx - aax0);

                            for (end = (aax1 <= x1) ? aax1 : x1; cx < end; cx++) {
                                tile[idx++] = _unsafe.getByte(addr); // [0-255]
                                addr += SIZE_BYTE;
                            }
                        }
                    }
                } else {
                    // RLE encoding:

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (rowAAx1[cy] > x0) { // last pixel exclusive

                        cx = rowAAx0[cy]; // inclusive
                        if (cx > x1) {
                            cx = x1;
                        }

                        // fill line start until first AA pixel rowAA exclusive:
                        for (end = x0; end < cx; end++) {
                            tile[idx++] = 0;
                        }

                        // get row address:
                        addr_row = addr_rowAA + rowAAChunkIndex[cy];
                        // get row end address:
                        addr_end = addr_row + rowAALen[cy]; // coded length

                        // reuse previous iteration position:
                        addr = addr_row + rowAAPos[cy];

                        last_addr = 0L;

                        while ((cx < x1) && (addr < addr_end)) {
                            // keep current position:
                            last_addr = addr;

                            // packed value:
                            packed = _unsafe.getInt(addr);

                            // last exclusive pixel x-coordinate:
                            cx1 = (packed >> 8);
                            // as bytes:
                            addr += SIZE_INT;

                            rx0 = cx;
                            if (rx0 < x0) {
                                rx0 = x0;
                            }
                            rx1 = cx = cx1;
                            if (rx1 > x1) {
                                rx1 = x1;
                                cx  = x1; // fix last x
                            }
                            // adjust runLen:
                            runLen = rx1 - rx0;

                            // ensure rx1 > rx0:
                            if (runLen > 0) {
                                packed &= 0xFF; // [0-255]

                                val = (byte) packed; // [0-255]
                                do {
                                    tile[idx++] = val;
                                } while (--runLen > 0);
                            }
                        }

                        // Update last position in RLE entries:
                        if (last_addr != 0L) {
                            // Fix x0:
                            rowAAx0[cy]  = cx; // inclusive
                            // Fix position:
                            rowAAPos[cy] = (last_addr - addr_row);
                        }
                    }
                }

                // fill line end
                while (cx < x1) {
                    tile[idx++] = 0;
                    cx++;
                }

                if (DO_TRACE) {
                    for (int i = idx - (x1 - x0); i < idx; i++) {
                        System.out.print(hex(tile[i], 2));
                    }
                    System.out.println();
                }

                idx += skipRowPixels;
            }
        break;

        case 2: // 0xFF
            // Fill full tile rows:
            Arrays.fill(tile, offset, offset + (y1 * rowstride), refVal);

            for (cy = y0; cy < y1; cy++) {
                // empty line (default)
                cx = x0;

                if (rowAAEnc[cy] == 0) {
                    // Raw encoding:

                    final int aax1 = rowAAx1[cy]; // exclusive

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (aax1 > x0) {
                        final int aax0 = rowAAx0[cy]; // inclusive

                        if (aax0 < x1) {
                            // note: cx is the cursor pointer in the tile array
                            // (left to right)
                            cx = aax0;

                            // ensure cx >= x0
                            if (cx <= x0) {
                                cx = x0;
                            } else {
                                // fill line start until first AA pixel rowAA exclusive:
                                for (end = x0; end < cx; end++) {
                                    tile[idx++] = 0;
                                }
                            }

                            // now: cx >= x0 and cx >= aax0

                            // Copy AA data (sum alpha data):
                            addr = addr_rowAA + rowAAChunkIndex[cy] + (cx - aax0);

                            for (end = (aax1 <= x1) ? aax1 : x1; cx < end; cx++) {
                                tile[idx++] = _unsafe.getByte(addr); // [0-255]
                                addr += SIZE_BYTE;
                            }
                        }
                    }
                } else {
                    // RLE encoding:

                    // quick check if there is AA data
                    // corresponding to this tile [x0; x1[
                    if (rowAAx1[cy] > x0) { // last pixel exclusive

                        cx = rowAAx0[cy]; // inclusive
                        if (cx > x1) {
                            cx = x1;
                        }

                        // fill line start until first AA pixel rowAA exclusive:
                        for (end = x0; end < cx; end++) {
                            tile[idx++] = 0;
                        }

                        // get row address:
                        addr_row = addr_rowAA + rowAAChunkIndex[cy];
                        // get row end address:
                        addr_end = addr_row + rowAALen[cy]; // coded length

                        // reuse previous iteration position:
                        addr = addr_row + rowAAPos[cy];

                        last_addr = 0L;

                        while ((cx < x1) && (addr < addr_end)) {
                            // keep current position:
                            last_addr = addr;

                            // packed value:
                            packed = _unsafe.getInt(addr);

                            // last exclusive pixel x-coordinate:
                            cx1 = (packed >> 8);
                            // as bytes:
                            addr += SIZE_INT;

                            rx0 = cx;
                            if (rx0 < x0) {
                                rx0 = x0;
                            }
                            rx1 = cx = cx1;
                            if (rx1 > x1) {
                                rx1 = x1;
                                cx  = x1; // fix last x
                            }
                            // adjust runLen:
                            runLen = rx1 - rx0;

                            // ensure rx1 > rx0:
                            if (runLen > 0) {
                                packed &= 0xFF; // [0-255]

                                if (packed == 0xFF)
                                {
                                    idx += runLen;
                                    continue;
                                }
                                val = (byte) packed; // [0-255]
                                do {
                                    tile[idx++] = val;
                                } while (--runLen > 0);
                            }
                        }

                        // Update last position in RLE entries:
                        if (last_addr != 0L) {
                            // Fix x0:
                            rowAAx0[cy]  = cx; // inclusive
                            // Fix position:
                            rowAAPos[cy] = (last_addr - addr_row);
                        }
                    }
                }

                // fill line end
                while (cx < x1) {
                    tile[idx++] = 0;
                    cx++;
                }

                if (DO_TRACE) {
                    for (int i = idx - (x1 - x0); i < idx; i++) {
                        System.out.print(hex(tile[i], 2));
                    }
                    System.out.println();
                }

                idx += skipRowPixels;
            }
        }

        nextTile();

        if (DO_MONITORS) {
            rdrStats.mon_ptg_getAlpha.stop();
        }
    }

    static String hex(int v, int d) {
        String s = Integer.toHexString(v);
        while (s.length() < d) {
            s = "0" + s;
        }
        return s.substring(0, d);
    }
}