public void encode()

in batik-codec/src/main/java/org/apache/batik/ext/awt/image/codec/png/PNGImageEncoder.java [858:1043]
148 lines of code
39 McCabe index (conditional complexity)

    public void encode(RenderedImage im) throws IOException {
        this.image = im;
        this.width = image.getWidth();
        this.height = image.getHeight();

        SampleModel sampleModel = image.getSampleModel();

        int[] sampleSize = sampleModel.getSampleSize();

        // Set bitDepth to a sentinel value
        this.bitDepth = -1;
        this.bitShift = 0;

        // Allow user to override the bit depth of gray images
        if (param instanceof PNGEncodeParam.Gray) {
            PNGEncodeParam.Gray paramg = (PNGEncodeParam.Gray)param;
            if (paramg.isBitDepthSet()) {
                this.bitDepth = paramg.getBitDepth();
            }

            if (paramg.isBitShiftSet()) {
                this.bitShift = paramg.getBitShift();
            }
        }

        // Get bit depth from image if not set in param
        if (this.bitDepth == -1) {
            // Get bit depth from channel 0 of the image

            this.bitDepth = sampleSize[0];
            // Ensure all channels have the same bit depth
            for (int i = 1; i < sampleSize.length; i++) {
                if (sampleSize[i] != bitDepth) {
                    throw new RuntimeException();
                }
            }

            // Round bit depth up to a power of 2
            if (bitDepth > 2 && bitDepth < 4) {
                bitDepth = 4;
            } else if (bitDepth > 4 && bitDepth < 8) {
                bitDepth = 8;
            } else if (bitDepth > 8 && bitDepth < 16) {
                bitDepth = 16;
            } else if (bitDepth > 16) {
                throw new RuntimeException();
            }
        }

        this.numBands = sampleModel.getNumBands();
        this.bpp = numBands*((bitDepth == 16) ? 2 : 1);

        ColorModel colorModel = image.getColorModel();
        if (colorModel instanceof IndexColorModel) {
            if (bitDepth < 1 || bitDepth > 8) {
                throw new RuntimeException();
            }
            if (sampleModel.getNumBands() != 1) {
                throw new RuntimeException();
            }

            IndexColorModel icm = (IndexColorModel)colorModel;
            int size = icm.getMapSize();

            redPalette = new byte[size];
            greenPalette = new byte[size];
            bluePalette = new byte[size];
            alphaPalette = new byte[size];

            icm.getReds(redPalette);
            icm.getGreens(greenPalette);
            icm.getBlues(bluePalette);
            icm.getAlphas(alphaPalette);

            this.bpp = 1;

            if (param == null) {
                param = createGrayParam(redPalette,
                                        greenPalette,
                                        bluePalette,
                                        alphaPalette);
            }

            // If param is still null, it can't be expressed as gray
            if (param == null) {
                param = new PNGEncodeParam.Palette();
            }

            if (param instanceof PNGEncodeParam.Palette) {
                // If palette not set in param, create one from the ColorModel.
                PNGEncodeParam.Palette parami = (PNGEncodeParam.Palette)param;
                if (parami.isPaletteSet()) {
                    int[] palette = parami.getPalette();
                    size = palette.length/3;

                    int index = 0;
                    for (int i = 0; i < size; i++) {
                        redPalette[i] = (byte)palette[index++];
                        greenPalette[i] = (byte)palette[index++];
                        bluePalette[i] = (byte)palette[index++];
                        alphaPalette[i] = (byte)255;
                    }
                }
                this.colorType = PNG_COLOR_PALETTE;
            } else if (param instanceof PNGEncodeParam.Gray) {
                redPalette = greenPalette = bluePalette = alphaPalette = null;
                this.colorType = PNG_COLOR_GRAY;
            } else {
                throw new RuntimeException();
            }
        } else if (numBands == 1) {
            if (param == null) {
                param = new PNGEncodeParam.Gray();
            }
            this.colorType = PNG_COLOR_GRAY;
        } else if (numBands == 2) {
            if (param == null) {
                param = new PNGEncodeParam.Gray();
            }

            if (param.isTransparencySet()) {
                skipAlpha = true;
                numBands = 1;
                if ((sampleSize[0] == 8) && (bitDepth < 8)) {
                    compressGray = true;
                }
                bpp = (bitDepth == 16) ? 2 : 1;
                this.colorType = PNG_COLOR_GRAY;
            } else {
                if (this.bitDepth < 8) {
                    this.bitDepth = 8;
                }
                this.colorType = PNG_COLOR_GRAY_ALPHA;
            }
        } else if (numBands == 3) {
            if (param == null) {
                param = new PNGEncodeParam.RGB();
            }
            this.colorType = PNG_COLOR_RGB;
        } else if (numBands == 4) {
            if (param == null) {
                param = new PNGEncodeParam.RGB();
            }
            if (param.isTransparencySet()) {
                skipAlpha = true;
                numBands = 3;
                bpp = (bitDepth == 16) ? 6 : 3;
                this.colorType = PNG_COLOR_RGB;
            } else {
                this.colorType = PNG_COLOR_RGB_ALPHA;
            }
        }

        interlace = param.getInterlacing();

        writeMagic();

        writeIHDR();

        writeCHRM();
        writeGAMA();
        writeICCP();
        writeSBIT();
        writeSRGB();

        writePLTE();

        writeHIST();
        writeTRNS();
        writeBKGD();

        writePHYS();
        writeSPLT();
        writeTIME();
        writeTEXT();
        writeZTXT();

        writePrivateChunks();

        writeIDAT();

        writeIEND();

        dataOutput.flush();
        dataOutput.close();
    }