Image compression method

Abstract

The invention relates to a method in image processing, wherein an image in digital form is in coding phase compressed, quantized by a quantization matrix (QL, QC) and coded by a coding matrix (HL 1, HK 1, HL 2 ), wherein one or more data frames are formed. In a decoding phase decoding, dequantization and decompression is carried out to the information comprised in the data frame. One or more matrices (QL, QC, HL 1, HK 1, HL 2 ) used in the coding phase are left out of the data frame, wherein the corresponding matrix is stored into coding device ( 8 ) performing the decoding phase.

1 . A method in image processing, in which method an image in digital form is in coding phase compressed, quantized by a quantization matrix (QL, QC) and coded by a coding matrix (HL 1 , HK 1 , HL 2 ), wherein one or more data frame is formed, and in decoding phase decoding, dequantization and decompression is carried out to the information comprised in the data frame, characterized in that one or more matrices (QL, QC, HL 1 , HK 1 , HL 2 ) used in the coding phase are left out of the data frame, wherein the corresponding matrix is stored into a coding device ( 8 ) performing the decoding phase.  
     
     
         2 . The method according to  claim 1 , characterized in that the compression is carried out with discrete cosine transform (DCT).  
     
     
         3 . The method according to  claim 1  or  2 , characterized in that the coding is carried out with variable length coding, such as Huffman coding.  
     
     
         4 . The method according to any of  claims 1  to  3 , characterized in that the compression is carried out in accordance with the JPEG standard compression.  
     
     
         5 . A device, preferably a mobile station ( 13 ), comprising means ( 8 ) for processing an image in digital form and means ( 12 ) for showing the image to the user, which image in digital form has in the coding phase been compressed, quantized by a quantization matrix (QL, QC) and coded by a coding matrix (HL 1 , HK 1 , HL 2 ) to form one or more data frames ( 300 ), and which image treating means ( 8 ) comprise means ( 9 ,  10 ,  11 ) for decoding, dequantization and decompression of the information comprised in the data frame ( 300 ), characterized in that the image processing means ( 8 ) further comprise means ( 14 ) with which the matrix (QL, QC, HL 1 , HK 1 , HL 2 ) used in the coding phase and left out of the data frame is stored and used in the decoding of image.  
     
     
         6 . The device ( 13 ) according to  claim 5 , characterized in that the image processing means ( 8 ) comprise an inverse discrete cosine transformer ( 11 ).  
     
     
         7 . The device ( 13 ) according to  claim 5  or  6 , characterized in that it further comprises image coding means ( 1 ), comprising means ( 2 ) for image compression, means ( 3 ) for quantization the image by a quantization matrix (QL, QC), means ( 4 ) for coding the image by coding matrix (HL 1 , HK 1 , HL 2 ) and means ( 5 ) for forming the data frame ( 300 ), wherein the data frame ( 300 ) is arranged to be formed without one or more matrices (QL, QC, HL 1 , HK 1 , HL 2 ).  
     
     
         8 . The device ( 13 ) according to any of  claims 5  to  7 , characterized in that the mobile station comprises means ( 6 ) for storing the data frame ( 300 ).