Patent attributes
There is provided with an image coding method including: splitting an image into a plurality of block images each having plural pixels; performing a Discrete Cosine Transform (DCT) processing on the block image to calculate DCT coefficients from the block image; determining whether the block image is in a flat state or non-flat state depending on the DCT coefficients calculated from the block image; specifying as quantization step sizes for first DCT coefficients which are DCT coefficients equivalent to one-dimensional DCT coefficient out of the calculated DCT coefficients, adjusting step sizes equal to or smaller than values of the first DCT coefficients and as quantization step sizes for second DCT coefficients other than the first DCT coefficients out of the calculated DCT coefficients, standard step sizes given beforehand, when the block image is in the flat state; and quantizing the calculated DCT coefficients with respective quantization step sizes specified.
