data size of compressed image when image compression is performed for the entire image plane of the image data equals to a prescribed desired data size and such that the compression ratio of the image data to the color data equals to or exceeds the compression ratio of the image data to the luminance data and an image compressing portion for performing image compression for the entire image plane of the image data in accordance with the compression ratios of the image data to the color and luminance data it is noted that a method of compressing image data and a digital camera using the image data compression apparatus are also claimed application_number US 10266498 A description a digital still camera according to an embodiment of the present invention will now be described with reference to the drawings referring to fig1 and 2 the digital still camera includes a ccd imager 1 to which a primary color filter 30 is mounted having row u00d7 column 480 u00d7 640 pixels and color filters of three primary colors r g and b arranged in a mosaic like pattern an a d analog to digital converter 2 digitizing r g and b image signals output from ccd imager 1 to image data a signal processing circuit 3 performing well known gamma control and white balance adjustment for the r g and b image data a dram 4 storing the image data for which the gamma control and white balance adjustment have been performed and a cpu central processing unit 5 calculating an optimum image compression ratio and in accordance with the compression ratio.