gifimagereader.java

来自「JAVA的一些源码 JAVA2 STANDARD EDITION DEVELO」· Java 代码 · 共 1,146 行 · 第 1/3 页

        // attempt to analyze the congruences.  If passPeriod and
        // sourceSubsamling are relatively prime, the period will be
        // their product.  If they share a common factor, either the
        // period will be equal to the larger value, or the sequences
        // will be completely disjoint, depending on the relationship
        // between passStart and sourceOffset.  Since we only have to do this
        // twice per image (once each for X and Y), it seems cheap enough
        // to do it the straightforward way.

        boolean gotPixel = false;
        int firstDst = -1;
        int secondDst = -1;
        int lastDst = -1;

        for (int i = 0; i < passExtent; i++) {
            int src = passStart + i*passPeriod;
            if (src < sourceOffset) {
                continue;
            }
            if ((src - sourceOffset) % sourceSubsampling != 0) {
                continue;
            }
            if (src >= sourceOffset + sourceExtent) {
                break;
            }

            int dst = destinationOffset +
                (src - sourceOffset)/sourceSubsampling;
            if (dst < dstMin) {
                continue;
            }
            if (dst > dstMax) {
                break;
            }

            if (!gotPixel) {
                firstDst = dst; // Record smallest valid pixel
                gotPixel = true;
            } else if (secondDst == -1) {
                secondDst = dst; // Record second smallest valid pixel
            }
            lastDst = dst; // Record largest valid pixel
        }

        vals[offset] = firstDst;

        // If we never saw a valid pixel, set width to 0
        if (!gotPixel) {
            vals[offset + 2] = 0;
        } else {
            vals[offset + 2] = lastDst - firstDst + 1;
        }

        // The period is given by the difference of any two adjacent pixels
        vals[offset + 4] = Math.max(secondDst - firstDst, 1);
    }

    /**
     * A utility method that computes the exact set of destination
     * pixels that will be written during a particular decoding pass.
     * The intent is to simplify the work done by readers in combining
     * the source region, source subsampling, and destination offset
     * information obtained from the <code>ImageReadParam</code> with
     * the offsets and periods of a progressive or interlaced decoding
     * pass.
     *
     * @param sourceRegion a <code>Rectangle</code> containing the
     * source region being read, offset by the source subsampling
     * offsets, and clipped against the source bounds, as returned by
     * the <code>getSourceRegion</code> method.
     * @param destinationOffset a <code>Point</code> containing the
     * coordinates of the upper-left pixel to be written in the
     * destination.
     * @param dstMinX the smallest X coordinate (inclusive) of the
     * destination <code>Raster</code>.
     * @param dstMinY the smallest Y coordinate (inclusive) of the
     * destination <code>Raster</code>.
     * @param dstMaxX the largest X coordinate (inclusive) of the destination
     * <code>Raster</code>.
     * @param dstMaxY the largest Y coordinate (inclusive) of the destination
     * <code>Raster</code>.
     * @param sourceXSubsampling the X subsampling factor.
     * @param sourceYSubsampling the Y subsampling factor.
     * @param passXStart the smallest source X coordinate (inclusive)
     * of the current progressive pass.
     * @param passYStart the smallest source Y coordinate (inclusive)
     * of the current progressive pass.
     * @param passWidth the width in pixels of the current progressive
     * pass.
     * @param passHeight the height in pixels of the current progressive
     * pass.
     * @param passPeriodX the X period (horizontal spacing between
     * pixels) of the current progressive pass.
     * @param passPeriodY the Y period (vertical spacing between
     * pixels) of the current progressive pass.
     *
     * @return an array of 6 <code>int</code>s containing the
     * destination min X, min Y, width, height, X period and Y period
     * of the region that will be updated.
     */
    private static int[] computeUpdatedPixels(Rectangle sourceRegion,
                                              Point destinationOffset,
                                              int dstMinX,
                                              int dstMinY,
                                              int dstMaxX,
                                              int dstMaxY,
                                              int sourceXSubsampling,
                                              int sourceYSubsampling,
                                              int passXStart,
                                              int passYStart,
                                              int passWidth,
                                              int passHeight,
                                              int passPeriodX,
                                              int passPeriodY) {
        int[] vals = new int[6];
        computeUpdatedPixels(sourceRegion.x, sourceRegion.width,
                             destinationOffset.x,
                             dstMinX, dstMaxX, sourceXSubsampling,
                             passXStart, passWidth, passPeriodX,
                             vals, 0);
        computeUpdatedPixels(sourceRegion.y, sourceRegion.height,
                             destinationOffset.y,
                             dstMinY, dstMaxY, sourceYSubsampling,
                             passYStart, passHeight, passPeriodY,
                             vals, 1);
        return vals;
    }

    private void startPass(int pass) {
        if (updateListeners == null) {
            return;
        }

        int y = 0;
        int yStep = 1;
        if (imageMetadata.interlaceFlag) {
            y = interlaceOffset[interlacePass];
            yStep = interlaceIncrement[interlacePass];
        }

        int[] vals =
            computeUpdatedPixels(sourceRegion,
                                 destinationOffset,
                                 destinationRegion.x, 
                                 destinationRegion.y,
                                 destinationRegion.x +
                                 destinationRegion.width - 1,
                                 destinationRegion.y +
                                 destinationRegion.height - 1,
                                 sourceXSubsampling,
                                 sourceYSubsampling,
                                 0,
                                 y,
                                 destinationRegion.width,
                                 (destinationRegion.height + yStep - 1)/yStep,
                                 1,
                                 yStep);

        // Initialized updateMinY and updateYStep
        this.updateMinY = vals[1];
        this.updateYStep = vals[5];

        // Inform IIOReadUpdateListeners of new pass
        int[] bands = { 0 };

        processPassStarted(theImage,
                           interlacePass,
                           sourceMinProgressivePass,
                           sourceMaxProgressivePass,
                           0,
                           updateMinY,
                           1,
                           updateYStep,
                           bands);
    }

    public BufferedImage read(int imageIndex, ImageReadParam param)
        throws IIOException {
        if (stream == null) {
            throw new IllegalStateException("Input not set!");
        }
        checkIndex(imageIndex);

        int index = locateImage(imageIndex);
        if (index != imageIndex) {
            throw new IndexOutOfBoundsException("imageIndex out of bounds!");
        }

        clearAbortRequest();
        readMetadata();

        // A null ImageReadParam means we use the default
        if (param == null) {
            param = getDefaultReadParam();
        }

        // Initialize the destination image
        Iterator imageTypes = getImageTypes(imageIndex);
        this.theImage = getDestination(param,
                                       imageTypes,
                                       imageMetadata.imageWidth,
                                       imageMetadata.imageHeight);
        this.theTile = theImage.getWritableTile(0, 0);
        this.width = imageMetadata.imageWidth;
        this.height = imageMetadata.imageHeight;
        this.streamX = 0;
        this.streamY = 0;
        this.rowsDone = 0;
        this.interlacePass = 0;

        // Get source region, taking subsampling offsets into account,
        // and clipping against the true source bounds
        
        this.sourceRegion = new Rectangle(0, 0, 0, 0);
        this.destinationRegion = new Rectangle(0, 0, 0, 0);
        computeRegions(param, width, height, theImage,
                       sourceRegion, destinationRegion);
        this.destinationOffset = new Point(destinationRegion.x,
                                           destinationRegion.y);

        this.sourceXSubsampling = param.getSourceXSubsampling();
        this.sourceYSubsampling = param.getSourceYSubsampling();
        this.sourceMinProgressivePass =
            Math.max(param.getSourceMinProgressivePass(), 0);
        this.sourceMaxProgressivePass =
            Math.min(param.getSourceMaxProgressivePass(), 3);

        this.destY = destinationRegion.y +
            (streamY - sourceRegion.y)/sourceYSubsampling;
        computeDecodeThisRow();

        // Inform IIOReadProgressListeners of start of image
        processImageStarted(imageIndex);
        startPass(0);

        this.rowBuf = new byte[width];

        try {
            // Read and decode the image data, fill in theImage
            this.initCodeSize = stream.readUnsignedByte();

            // Read first data block
            this.blockLength = stream.readUnsignedByte();
            int left = blockLength;
            int off = 0;
            while (left > 0) {
                int nbytes = stream.read(block, off, left);
                left -= nbytes;
                off += nbytes;
            }

            this.bitPos = 0;
            this.nextByte = 0;
            this.lastBlockFound = false;
            this.interlacePass = 0;

            // Init 32-bit buffer
            initNext32Bits();

            this.clearCode = 1 << initCodeSize;
            this.eofCode = clearCode + 1;

            int code, oldCode = 0;

            int[] prefix = new int[4096];
            byte[] suffix = new byte[4096];
            byte[] initial = new byte[4096];
            int[] length = new int[4096];
            byte[] string = new byte[4096];

            initializeStringTable(prefix, suffix, initial, length);
            int tableIndex = (1 << initCodeSize) + 2;
            int codeSize = initCodeSize + 1;
            int codeMask = (1 << codeSize) - 1;

            while (!abortRequested()) {
                code = getCode(codeSize, codeMask);

                if (code == clearCode) {
                    initializeStringTable(prefix, suffix, initial, length);
                    tableIndex = (1 << initCodeSize) + 2;
                    codeSize = initCodeSize + 1;
                    codeMask = (1 << codeSize) - 1;

                    code = getCode(codeSize, codeMask);
                    if (code == eofCode) {
                        // Inform IIOReadProgressListeners of end of image
                        processImageComplete();
                        return theImage;
                    }
                } else if (code == eofCode) {
                    // Inform IIOReadProgressListeners of end of image
                    processImageComplete();
                    return theImage;
                } else {
                    int newSuffixIndex;
                    if (code < tableIndex) {
                        newSuffixIndex = code;
                    } else { // code == tableIndex
                        newSuffixIndex = oldCode;
                        if (code != tableIndex) {
                            // warning - code out of sequence
                            // possibly data corruption
                            processWarningOccurred("Out-of-sequence code!");
                        }
                    }

                    int ti = tableIndex;
                    int oc = oldCode;

                    prefix[ti] = oc;
                    suffix[ti] = initial[newSuffixIndex];
                    initial[ti] = initial[oc];
                    length[ti] = length[oc] + 1;
                    
                    ++tableIndex;
                    if ((tableIndex == (1 << codeSize)) &&
                        (tableIndex < 4096)) {
                        ++codeSize;
                        codeMask = (1 << codeSize) - 1;
                    }
                }

                // Reverse code
                int c = code;
                int len = length[c];
                for (int i = len - 1; i >= 0; i--) {
                    string[i] = suffix[c];
                    c = prefix[c];
                }
                
                outputPixels(string, len);
                oldCode = code;
            }

            processReadAborted();
            return theImage;
        } catch (IOException e) {
            e.printStackTrace();
            throw new IIOException("I/O error reading image!", e);
        }
    }    
    
    /**
     * Remove all settings including global settings such as
     * <code>Locale</code>s and listeners, as well as stream settings.
     */
    public void reset() {
        super.reset();
        resetStreamSettings();
    }

    /**
     * Remove local settings based on parsing of a stream.
     */
    private void resetStreamSettings() {
        gotHeader = false;
        streamMetadata = null;
        currIndex = -1;
        imageMetadata = null;
        imageStartPosition = new ArrayList();
        numImages = -1;

        // No need to reinitialize 'block'
        blockLength = 0;
        bitPos = 0;
        nextByte = 0;

        next32Bits = 0;
        lastBlockFound = false;

        theImage = null;
        theTile = null;
        width = -1;
        height = -1;
        streamX = -1;
        streamY = -1;
        rowsDone = 0;
        interlacePass = 0;
    }
}