inverse discrete cosine transform (IDCT)
The DCT transform (Discrete Cosine Transform) is used in image compression when pixel graphics are converted to JPEG. When converting JPEG to pixel graphics, on the other hand, the IDCT transform (Inverse Discrete Cosine Transform) is used.
It takes over the inverse part of the DCT transformation and, after de-quantizing the quantized coefficient matrix, converts its values by means of DCT basis functions into the brightness and color signals, from which the RGB signals of the pixel graphics are then obtained.