private void readMcu()

in src/main/java/org/apache/commons/imaging/formats/jpeg/decoder/JpegDecoder.java [214:296]
73 lines of code
16 McCabe index (conditional complexity)

    private void readMcu(final JpegInputStream is, final int[] preds, final Block[] mcu) throws ImagingException {
        for (int i = 0; i < sosSegment.numberOfComponents; i++) {
            final SosSegment.Component scanComponent = sosSegment.getComponents(i);
            SofnSegment.Component frameComponent = null;
            for (int j = 0; j < sofnSegment.numberOfComponents; j++) {
                if (sofnSegment.getComponents(j).componentIdentifier == scanComponent.scanComponentSelector) {
                    frameComponent = sofnSegment.getComponents(j);
                    break;
                }
            }
            if (frameComponent == null) {
                throw new ImagingException("Invalid component");
            }
            final Block fullBlock = mcu[i];
            for (int y = 0; y < frameComponent.verticalSamplingFactor; y++) {
                for (int x = 0; x < frameComponent.horizontalSamplingFactor; x++) {
                    Arrays.fill(zz, 0);
                    // page 104 of T.81
                    final int t = decode(is, huffmanDCTables[scanComponent.dcCodingTableSelector]);
                    int diff = receive(t, is);
                    diff = extend(diff, t);
                    zz[0] = preds[i] + diff;
                    preds[i] = zz[0];

                    // "Decode_AC_coefficients", figure F.13, page 106 of T.81
                    int k = 1;
                    while (true) {
                        final int rs = decode(is, huffmanACTables[scanComponent.acCodingTableSelector]);
                        final int ssss = rs & 0xf;
                        final int rrrr = rs >> 4;
                        final int r = rrrr;

                        if (ssss == 0) {
                            if (r != 15) {
                                break;
                            }
                            k += 16;
                        } else {
                            k += r;

                            // "Decode_ZZ(k)", figure F.14, page 107 of T.81
                            zz[k] = receive(ssss, is);
                            zz[k] = extend(zz[k], ssss);

                            if (k == 63) {
                                break;
                            }
                            k++;
                        }
                    }

                    final int shift = 1 << sofnSegment.precision - 1;
                    final int max = (1 << sofnSegment.precision) - 1;

                    final float[] scaledQuantizationTable = scaledQuantizationTables[frameComponent.quantTabDestSelector];
                    ZigZag.zigZagToBlock(zz, blockInt);
                    for (int j = 0; j < 64; j++) {
                        block[j] = blockInt[j] * scaledQuantizationTable[j];
                    }
                    Dct.inverseDct8x8(block);

                    int dstRowOffset = 8 * y * 8 * frameComponent.horizontalSamplingFactor + 8 * x;
                    int srcNext = 0;
                    for (int yy = 0; yy < 8; yy++) {
                        for (int xx = 0; xx < 8; xx++) {
                            float sample = block[srcNext++];
                            sample += shift;
                            final int result;
                            if (sample < 0) {
                                result = 0;
                            } else if (sample > max) {
                                result = max;
                            } else {
                                result = fastRound(sample);
                            }
                            fullBlock.samples[dstRowOffset + xx] = result;
                        }
                        dstRowOffset += 8 * frameComponent.horizontalSamplingFactor;
                    }
                }
            }
        }
    }