Abstract: A JPEG decoder having a scaling function includes an inverse discrete cosine transform block, wherein the JPEG decoder selectively performs an inverse discrete cosine transform on a part of pixel data of a macroblock through the inverse discrete cosine transform block and outputs a scaled image file. The JPEG decoder and the scaling method using the JPEG decoder increase a decoding speed, thereby enabling an image to be output in real time, especially when the JPEG decoder and/or the scaling method are applied to a mobile field. Also, the JPEG decoder and the scaling method using the JPEG decoder can achieve an efficient scaling, even without a separate circuit for scaling, thereby reducing a circuit size and the number of components.

Abstract: A JPEG decoder having a scaling function includes an inverse discrete cosine transform block, wherein the JPEG decoder selectively performs an inverse discrete cosine transform on a part of pixel data of a macroblock through the inverse discrete cosine transform block and outputs a scaled image file. The JPEG decoder and the scaling method using the JPEG decoder increase a decoding speed, thereby enabling an image to be output in real time, especially when the JPEG decoder and/or the scaling method are applied to a mobile field. Also, the JPEG decoder and the scaling method using the JPEG decoder can achieve an efficient scaling, even without a separate circuit for scaling, thereby reducing a circuit size and the number of components.

Abstract: An image rotation method without using a memory includes the steps of: reading, by a JPEG encoder, an input image having m×n macroblocks (wherein “m” and “n” are natural numbers); rotating image data of the respective macroblocks by a predetermined angle in a predetermined direction when encoding in the JPEG encoder; assigning and inputting a sequence of each rotated image data when encoding in the JPEG encoder; instructing the macroblocks to be output in a sequence changed from an initial input sequence of the macroblocks through use of a program when decoding in a JPEG decoder; and outputting an image rotated by the predetermined angle in the predetermined direction.