METHOD OF CONTROLLING OUTPUT FILE SIZE FROM IMAGE JPEG COMPRESSION

摘要

FIELD: data processing.;SUBSTANCE: invention relates to compressing digital images. Method of controlling speed in JPEG compression of a digital image includes the stages, at which received are coefficients of discrete cosine transform (DCT) obtained as the result of direct DCT application to a digital image; generated are quantization tables (QT) using the received DCT coefficients by iterative estimating the scaling factor to create scaled QT, checking whether the first condition of the iterations completion is true, herewith the first condition of the iterations completion is considered to be true, when the complete actual number of bits calculated for all the colour planes is within the range of tolerance defined, at least, on the basis of the target size of the output file for the JPEG-compressed image, and if the said condition is false, the scaling factor is updated, as well as the said variables, including boundary values of the first range of the scaling factor.;EFFECT: providing a digital image JPEG compression speed control by means of generating a set of quantization tables.;13 cl, 9 dwg