jpegimagereader.java

java1.6众多例子参考

        
        ArrayList list = new ArrayList(1);

        switch (colorSpaceCode) {
        case JPEG.JCS_GRAYSCALE:
            list.add(raw);
            list.add(getImageType(JPEG.JCS_RGB));
            break;
        case JPEG.JCS_RGB:
            list.add(raw);
            list.add(getImageType(JPEG.JCS_GRAYSCALE));
            if (JPEG.JCS.YCC != null) {
                list.add(getImageType(JPEG.JCS_YCC));
            }
            break;
        case JPEG.JCS_RGBA:
            list.add(raw);
            break;
        case JPEG.JCS_YCC:
            if (raw != null) {  // Might be null if PYCC.pf not installed
                list.add(raw);
                list.add(getImageType(JPEG.JCS_RGB));
            }
            break;
        case JPEG.JCS_YCCA:
            if (raw != null) {  // Might be null if PYCC.pf not installed
                list.add(raw);
            }
            break;
        case JPEG.JCS_YCbCr:
            // As there is no YCbCr ColorSpace, we can't support
            // the raw type.

            // due to 4705399, use RGB as default in order to avoid
            // slowing down of drawing operations with result image.
            list.add(getImageType(JPEG.JCS_RGB));

            if (iccCS != null) {
                list.add(ImageTypeSpecifier.createInterleaved
                         (iccCS,
                          JPEG.bOffsRGB,  // Assume it's for RGB
                          DataBuffer.TYPE_BYTE,
                          false,
                          false));

            }

            list.add(getImageType(JPEG.JCS_GRAYSCALE));
            if (JPEG.JCS.YCC != null) { // Might be null if PYCC.pf not installed
                list.add(getImageType(JPEG.JCS_YCC));
            }
            break;
        case JPEG.JCS_YCbCrA:  // Default is to convert to RGBA
            // As there is no YCbCr ColorSpace, we can't support
            // the raw type.
            list.add(getImageType(JPEG.JCS_RGBA));
            break;
        }
        
        return list.iterator();
    }

    /**
     * Checks the implied color conversion between the stream and
     * the target image, altering the IJG output color space if necessary. 
     * If a java color conversion is required, then this sets up 
     * <code>convert</code>.
     * If bands are being rearranged at all (either source or destination
     * bands are specified in the param), then the default color 
     * conversions are assumed to be correct.
     * Throws an IIOException if there is no conversion available.
     */ 
    private void checkColorConversion(BufferedImage image, 
                                      ImageReadParam param) 
        throws IIOException {

        // If we are rearranging channels at all, the default
        // conversions remain in place.  If the user wants 
        // raw channels then he should do this while reading
        // a Raster.
        if (param != null) {
            if ((param.getSourceBands() != null) || 
                (param.getDestinationBands() != null)) {
                // Accept default conversions out of decoder, silently
                return;
            }
        }

        // XXX - We do not currently support any indexed color models,
        // though we could, as IJG will quantize for us.
        // This is a performance and memory-use issue, as
        // users can read RGB and then convert to indexed in Java.

        ColorModel cm = image.getColorModel();

        if (cm instanceof IndexColorModel) {
            throw new IIOException("IndexColorModel not supported");
        }
        
        // Now check the ColorSpace type against outColorSpaceCode
        // We may want to tweak the default
        ColorSpace cs = cm.getColorSpace();
        int csType = cs.getType();
        convert = null;
        switch (outColorSpaceCode) {
        case JPEG.JCS_GRAYSCALE:  // Its gray in the file
            if  (csType == ColorSpace.TYPE_RGB) { // We want RGB
                // IJG can do this for us more efficiently
                setOutColorSpace(structPointer, JPEG.JCS_RGB);
            } else if (csType != ColorSpace.TYPE_GRAY) {
                throw new IIOException("Incompatible color conversion");
            }
            break;
        case JPEG.JCS_RGB:  // IJG wants to go to RGB
            if (csType ==  ColorSpace.TYPE_GRAY) {  // We want gray
                if (colorSpaceCode == JPEG.JCS_YCbCr) {
                    // If the jpeg space is YCbCr, IJG can do it
                    setOutColorSpace(structPointer, JPEG.JCS_GRAYSCALE);
                }
            } else if ((iccCS != null) && 
                       (cm.getNumComponents() == numComponents) &&
                       (cs != iccCS)) {  
                // We have an ICC profile but it isn't used in the dest
                // image.  So convert from the profile cs to the target cs
                convert = new ColorConvertOp(iccCS, cs, null);
                // Leave IJG conversion in place; we still need it
            } else if ((iccCS == null) &&
                       (!cs.isCS_sRGB()) &&
                       (cm.getNumComponents() == numComponents)) {
                // Target isn't sRGB, so convert from sRGB to the target
                convert = new ColorConvertOp(JPEG.JCS.sRGB, cs, null);
            } else if (csType != ColorSpace.TYPE_RGB) {
                throw new IIOException("Incompatible color conversion");
            }
            break;
        case JPEG.JCS_RGBA:
            // No conversions available; image must be RGBA
            if ((csType != ColorSpace.TYPE_RGB) ||
                (cm.getNumComponents() != numComponents)) {
                throw new IIOException("Incompatible color conversion");
            }
            break;
        case JPEG.JCS_YCC:
            if (JPEG.JCS.YCC == null) { // We can't do YCC at all
                throw new IIOException("Incompatible color conversion");
            }
            if ((cs != JPEG.JCS.YCC) &&
                (cm.getNumComponents() == numComponents)) {
                convert = new ColorConvertOp(JPEG.JCS.YCC, cs, null);
            }
            break;
        case JPEG.JCS_YCCA:
            // No conversions available; image must be YCCA
            if ((JPEG.JCS.YCC == null) || // We can't do YCC at all
                (cs != JPEG.JCS.YCC) ||
                (cm.getNumComponents() != numComponents)) {
                throw new IIOException("Incompatible color conversion");
            }
            break;
        default:
            // Anything else we can't handle at all
            throw new IIOException("Incompatible color conversion");
        }
    }

    /** 
     * Set the IJG output space to the given value.  The library will
     * perform the appropriate colorspace conversions.
     */
    private native void setOutColorSpace(long structPointer, int id);

    /////// End of Color Conversion & Image Types
    
    public ImageReadParam getDefaultReadParam() {
        return new JPEGImageReadParam();
    }

    public IIOMetadata getStreamMetadata() throws IOException {
        if (!tablesOnlyChecked) {
            checkTablesOnly();
        }
        return streamMetadata;
    }

    public IIOMetadata getImageMetadata(int imageIndex)
        throws IOException {

        // imageMetadataIndex will always be either a valid index or
        // -1, in which case imageMetadata will not be null.
        // So we can leave checking imageIndex for gotoImage.
        if ((imageMetadataIndex == imageIndex)
            && (imageMetadata != null)) {
            return imageMetadata;
        }

        gotoImage(imageIndex);
        
        imageMetadata = new JPEGMetadata(false, false, iis, this);
        
        imageMetadataIndex = imageIndex;

        return imageMetadata;
        
    }

    public BufferedImage read(int imageIndex, ImageReadParam param)
        throws IOException {
        try {
            readInternal(imageIndex, param, false);
        } catch (RuntimeException e) {
            resetLibraryState(structPointer);
            throw e;
        } catch (IOException e) {
            resetLibraryState(structPointer);
            throw e;
        }
        BufferedImage ret = image;
        image = null;  // don't keep a reference here
        return ret;
    }

    private Raster readInternal(int imageIndex, 
                                ImageReadParam param,
                                boolean wantRaster) throws IOException {
        readHeader(imageIndex, false);
        
        WritableRaster imRas = null;
        int numImageBands = 0;

        if (!wantRaster){
            // Can we read this image?
            Iterator imageTypes = getImageTypes(imageIndex);
            if (imageTypes.hasNext() == false) {
                throw new IIOException("Unsupported Image Type");
            }

            image = getDestination(param, imageTypes, width, height);
            imRas = image.getRaster();

            // The destination may still be incompatible.

            numImageBands = image.getSampleModel().getNumBands();

            // Check whether we can handle any implied color conversion

            // Throws IIOException if the stream and the image are
            // incompatible, and sets convert if a java conversion
            // is necessary
            checkColorConversion(image, param);

            // Check the source and destination bands in the param
            checkReadParamBandSettings(param, numComponents, numImageBands);
        } else {
            // Set the output color space equal to the input colorspace
            // This disables all conversions
            setOutColorSpace(structPointer, colorSpaceCode);
            image = null;
        }

        // Create an intermediate 1-line Raster that will hold the decoded,
        // subsampled, clipped, band-selected image data in a single
        // byte-interleaved buffer.  The above transformations
        // will occur in C for performance.  Every time this Raster
        // is filled we will call back to acceptPixels below to copy
        // this to whatever kind of buffer our image has.

        int [] srcBands = JPEG.bandOffsets[numComponents-1];
        int numRasterBands = (wantRaster ? numComponents : numImageBands);
        destinationBands = null;

        Rectangle srcROI = new Rectangle(0, 0, 0, 0);
        destROI = new Rectangle(0, 0, 0, 0);
        computeRegions(param, width, height, image, srcROI, destROI);

        int periodX = 1;
        int periodY = 1;

        minProgressivePass = 0;
        maxProgressivePass = Integer.MAX_VALUE;

        if (param != null) {
            periodX = param.getSourceXSubsampling();
            periodY = param.getSourceYSubsampling();

            int[] sBands = param.getSourceBands();
            if (sBands != null) {
                srcBands = sBands;
                numRasterBands = srcBands.length;
            }
            if (!wantRaster) {  // ignore dest bands for Raster
                destinationBands = param.getDestinationBands();
            }

            minProgressivePass = param.getSourceMinProgressivePass();
            maxProgressivePass = param.getSourceMaxProgressivePass();

            if (param instanceof JPEGImageReadParam) {
                JPEGImageReadParam jparam = (JPEGImageReadParam) param;
                if (jparam.areTablesSet()) {
                    abbrevQTables = jparam.getQTables();
                    abbrevDCHuffmanTables = jparam.getDCHuffmanTables();
                    abbrevACHuffmanTables = jparam.getACHuffmanTables();
                }
            }
        }

        int lineSize = destROI.width*numRasterBands;
        
        buffer = new DataBufferByte(lineSize);

        int [] bandOffs = JPEG.bandOffsets[numRasterBands-1];
        
        raster = Raster.createInterleavedRaster(buffer, 
                                                destROI.width, 1, 
                                                lineSize,
                                                numRasterBands,
                                                bandOffs,
                                                null);
        
        // Now that we have the Raster we'll decode to, get a view of the
        // target Raster that will permit a simple setRect for each scanline
        if (wantRaster) {
            target =  Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, 
                                                     destROI.width,
                                                     destROI.height,
                                                     lineSize,
                                                     numRasterBands,
                                                     bandOffs,
                                                     null);
        } else {
	    target = imRas;
        }
        int [] bandSizes = target.getSampleModel().getSampleSize();

        /*
         * If the process is sequential, and we have restart markers, 
         * we could skip to the correct restart marker, if the library
         * lets us.  That's an optimization to investigate later.
         */

        // Check for update listeners (don't call back if none)
        boolean callbackUpdates = ((updateListeners != null) 
                                   || (progressListeners != null));

        // Set up progression data
        initProgressData();
        // if we have a metadata object, we can count the scans
        // and set knownPassCount
        if (imageIndex == imageMetadataIndex) { // We have metadata
            knownPassCount = 0;
            for (Iterator iter = imageMetadata.markerSequence.iterator();
                 iter.hasNext();) {
                if (iter.next() instanceof SOSMarkerSegment) {