An image coding method for run-length coding (RLC), including quantizing a coefficient string representing a plurality of pixel values to generate a first quantization coefficient string, determining a cutoff quantization coefficient in the first quantization coefficient string, discarding a part of quantization coefficients of the first quantization coefficient string according to the cutoff quantization coefficient, and forming remaining quantization coefficients of the first quantization coefficient string as a second quantization coefficient string, and performing image coding to the second quantization coefficient string with the RLC.