A method of coding an original image, including: partitioning (S110) the original image into blocks; determining (S120) a coding condition for a current one of the blocks; and coding (S130) the current block according to the determined coding condition, wherein the determining (S120) of the coding condition for the current block includes calculating (S210) a first spatial-activity value indicating complexity of at least a part of regions of the current block; comparing (S220) the first spatial-activity value with a first predetermined threshold value; determining (S230), as the coding condition for the current block, a first coding condition for small partitioning size, when the first spatial-activity value is smaller than the first predetermined threshold value; and determining (S240), as the coding condition for the current block, a second coding condition for large partitioning size, when the first spatial-activity value is equal to or larger than the first predetermined threshold value.