Patent ID: 8805108

Claim:
A JPEG decoder having a scaling function, the JPEG decoder comprising a dequantization block and an integrated inverse discrete cosine transform (IDCT) block, wherein the JPEG decoder is configured to perform an IDCT on a part of pixel data of a macroblock using the integrated IDCT block to control capacity and resolution of a resultant image file when decoding encoded data, and to output the decoded and scaled image file, wherein the dequantization block is configured to: dequantize at least a portion of pixel data of a macroblock; select, based on a scaling control signal, dequantized pixel data of the macroblock to output to the IDCT block; and output the selected pixel data to the IDCT block, wherein the IDCT block comprises a first IDCT unit, an orthogonal transform unit, and a second IDCT unit, wherein the first IDCT unit is configured to: select, based on the scaling control signal, pixel data output from the dequantization block comprising one or more selected columns among multiple columns of the macroblock such that a first IDCT is only performed on a portion of the columns of the macroblock, wherein when more than one column is selected to perform the first IDCT, no selected column is adjacent to another selected column; and perform the first IDCT on the selected pixel data output from the dequantization block; wherein the orthogonal transform unit is configured to perform an orthogonal transform on the pixel data subjected to the first IDCT to transpose rows and columns of the macroblock, and wherein the second IDCT unit is configured to: select, based on the scaling control signal, only data of one or more selected columns among multiple columns output from the orthogonal transform unit such that a second IDCT is only performed on a portion of the columns of the macroblock, wherein when more than one column is selected to perform the second IDCT, no selected column is adjacent to another selected column, further wherein only rows within the selected column which were subjected to the first IDCT are subjected to the second IDCT such that the number of columns subjected to the first IDCT equals the number of rows per column that are subjected to the second IDCT; and perform the second IDCT on the selected only a portion of the orthogonally transformed pixel data subjected to the first IDCT.