java.lang.Object
org.apache.commons.imaging.formats.jpeg.decoder.Dct

final class Dct extends Object
  • Field Details

    • DCT_SCALING_FACTORS

      private static final float[] DCT_SCALING_FACTORS
    • IDCT_SCALING_FACTORS

      private static final float[] IDCT_SCALING_FACTORS
    • A1

      private static final float A1
    • A2

      private static final float A2
    • A3

      private static final float A3
    • A4

      private static final float A4
    • A5

      private static final float A5
    • C2

      private static final float C2
    • C4

      private static final float C4
    • C6

      private static final float C6
    • Q

      private static final float Q
    • R

      private static final float R
  • Constructor Details

    • Dct

      private Dct()
  • Method Details

    • scaleQuantizationVector

      public static void scaleQuantizationVector(float[] vector)
    • scaleDequantizationVector

      public static void scaleDequantizationVector(float[] vector)
    • scaleQuantizationMatrix

      public static void scaleQuantizationMatrix(float[] matrix)
    • scaleDequantizationMatrix

      public static void scaleDequantizationMatrix(float[] matrix)
    • forwardDCT8

      public static void forwardDCT8(float[] vector)
      Fast forward Dct using AA&N. Taken from the book "JPEG still image data compression standard", by Pennebaker and Mitchell, chapter 4, figure "4-8".
    • forwardDCT8x8

      public static void forwardDCT8x8(float[] matrix)
    • inverseDCT8

      public static void inverseDCT8(float[] vector)
      Fast inverse Dct using AA&N. This is taken from the beautiful http://vsr.finermatik.tu-chemnitz.de/~jan/MPEG/HTML/IDCT.html which gives easy equations and properly explains constants and scaling factors. Terms have been inlined and the negation optimized out of existence.
    • inverseDCT8x8

      public static void inverseDCT8x8(float[] matrix)