@Override
    public BufferedImage getBufferedImage(final ByteSource byteSource, final PngImagingParameters params) throws ImagingException, IOException {

        final List<PngChunk> chunks = readChunks(byteSource,
                new ChunkType[] { ChunkType.IHDR, ChunkType.PLTE, ChunkType.IDAT, ChunkType.tRNS, ChunkType.iCCP, ChunkType.gAMA, ChunkType.sRGB, }, false);

        if (chunks.isEmpty()) {
            throw new ImagingException("PNG: no chunks");
        }

        final List<PngChunk> IHDRs = filterChunks(chunks, ChunkType.IHDR);
        if (IHDRs.size() != 1) {
            throw new ImagingException("PNG contains more than one Header");
        }

        final PngChunkIhdr pngChunkIHDR = (PngChunkIhdr) IHDRs.get(0);

        final List<PngChunk> PLTEs = filterChunks(chunks, ChunkType.PLTE);
        if (PLTEs.size() > 1) {
            throw new ImagingException("PNG contains more than one Palette");
        }

        PngChunkPlte pngChunkPLTE = null;
        if (PLTEs.size() == 1) {
            pngChunkPLTE = (PngChunkPlte) PLTEs.get(0);
        }

        final List<PngChunk> IDATs = filterChunks(chunks, ChunkType.IDAT);
        if (IDATs.isEmpty()) {
            throw new ImagingException("PNG missing image data");
        }

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        for (final PngChunk IDAT : IDATs) {
            final PngChunkIdat pngChunkIDAT = (PngChunkIdat) IDAT;
            final byte[] bytes = pngChunkIDAT.getBytes();
            // System.out.println(i + ": bytes: " + bytes.length);
            baos.write(bytes);
        }

        final byte[] compressed = baos.toByteArray();

        baos = null;

        AbstractTransparencyFilter abstractTransparencyFilter = null;

        final List<PngChunk> tRNSs = filterChunks(chunks, ChunkType.tRNS);
        if (!tRNSs.isEmpty()) {
            final PngChunk pngChunktRNS = tRNSs.get(0);
            abstractTransparencyFilter = getTransparencyFilter(pngChunkIHDR.getPngColorType(), pngChunktRNS);
        }

        ICC_Profile iccProfile = null;
        GammaCorrection gammaCorrection = null;
        {
            final List<PngChunk> sRGBs = filterChunks(chunks, ChunkType.sRGB);
            final List<PngChunk> gAMAs = filterChunks(chunks, ChunkType.gAMA);
            final List<PngChunk> iCCPs = filterChunks(chunks, ChunkType.iCCP);
            if (sRGBs.size() > 1) {
                throw new ImagingException("PNG: unexpected sRGB chunk");
            }
            if (gAMAs.size() > 1) {
                throw new ImagingException("PNG: unexpected gAMA chunk");
            }
            if (iCCPs.size() > 1) {
                throw new ImagingException("PNG: unexpected iCCP chunk");
            }

            if (sRGBs.size() == 1) {
                // no color management necessary.
                if (LOGGER.isLoggable(Level.FINEST)) {
                    LOGGER.finest("sRGB, no color management necessary.");
                }
            } else if (iCCPs.size() == 1) {
                if (LOGGER.isLoggable(Level.FINEST)) {
                    LOGGER.finest("iCCP.");
                }

                final PngChunkIccp pngChunkiCCP = (PngChunkIccp) iCCPs.get(0);
                final byte[] bytes = pngChunkiCCP.getUncompressedProfile();

                try {
                    iccProfile = ICC_Profile.getInstance(bytes);
                } catch (final IllegalArgumentException iae) {
                    throw new ImagingException("The image data does not correspond to a valid ICC Profile", iae);
                }
            } else if (gAMAs.size() == 1) {
                final PngChunkGama pngChunkgAMA = (PngChunkGama) gAMAs.get(0);
                final double gamma = pngChunkgAMA.getGamma();

                // charles: what is the correct target value here?
                // double targetGamma = 2.2;
                final double targetGamma = 1.0;
                final double diff = Math.abs(targetGamma - gamma);
                if (diff >= 0.5) {
                    gammaCorrection = new GammaCorrection(gamma, targetGamma);
                }

                if (gammaCorrection != null && pngChunkPLTE != null) {
                    pngChunkPLTE.correct(gammaCorrection);
                }

            }
        }

        {
            final int width = pngChunkIHDR.getWidth();
            final int height = pngChunkIHDR.getHeight();
            final PngColorType pngColorType = pngChunkIHDR.getPngColorType();
            final int bitDepth = pngChunkIHDR.getBitDepth();

            if (pngChunkIHDR.getFilterMethod() != 0) {
                throw new ImagingException("PNG: unknown FilterMethod: " + pngChunkIHDR.getFilterMethod());
            }

            final int bitsPerPixel = bitDepth * pngColorType.getSamplesPerPixel();

            final boolean hasAlpha = pngColorType.hasAlpha() || abstractTransparencyFilter != null;

            BufferedImage result;
            if (pngColorType.isGreyscale()) {
                result = getBufferedImageFactory(params).getGrayscaleBufferedImage(width, height, hasAlpha);
            } else {
                result = getBufferedImageFactory(params).getColorBufferedImage(width, height, hasAlpha);
            }

            final ByteArrayInputStream bais = new ByteArrayInputStream(compressed);
            final InflaterInputStream iis = new InflaterInputStream(bais);

            final AbstractScanExpediter abstractScanExpediter;

            switch (pngChunkIHDR.getInterlaceMethod()) {
            case NONE:
                abstractScanExpediter = new ScanExpediterSimple(width, height, iis, result, pngColorType, bitDepth, bitsPerPixel, pngChunkPLTE, gammaCorrection,
                        abstractTransparencyFilter);
                break;
            case ADAM7:
                abstractScanExpediter = new ScanExpediterInterlaced(width, height, iis, result, pngColorType, bitDepth, bitsPerPixel, pngChunkPLTE,
                        gammaCorrection, abstractTransparencyFilter);
                break;
            default:
                throw new ImagingException("Unknown InterlaceMethod: " + pngChunkIHDR.getInterlaceMethod());
            }

            abstractScanExpediter.drive();

            if (iccProfile != null) {
                final boolean isSrgb = new IccProfileParser().isSrgb(iccProfile);
                if (!isSrgb) {
                    final ICC_ColorSpace cs = new ICC_ColorSpace(iccProfile);

                    final ColorModel srgbCM = ColorModel.getRGBdefault();
                    final ColorSpace csSrgb = srgbCM.getColorSpace();

                    result = new ColorTools().convertBetweenColorSpaces(result, cs, csSrgb);
                }
            }

            return result;

        }

    }
Constructs a new instance with the big-endian byte order.
src/main/java/org/apache/commons/imaging/formats/png/PngImageParser.java