Color converting method and apparatus and image processing method and apparatus

A color converting apparatus for converting inputted color information by using a rewritable lookup table, comprising:

• measuring means for measuring occurrence frequencies of output color data of said lookup table;
• data obtaining means for obtaining table data which makes a dispersion of the occurrence frequencies of said output color data lie within a predetermined range on the basis of the occurrence frequency of each color which was measured by said measuring means;
• and
• writing means for writing said table data obtained by said data obtaining means into said lookup table,
• wherein said lookup table converts input colors into colors of a number smaller than the number of input colors and outputs, and
• wherein when the dispersion of the occurrence frequency of each color is equal to or larger than a predetermined value, said data obtaining means selects at least one of the color of a large occurrence frequency and the color of a small occurrence frequency and obtains table data such as to narrow an input width of said color of the large occurrence frequency and to widen an input width of said color of the small occurrence frequency.

A color converting method, comprising:

• a converting step of converting color information by using a lookup table formed initially according to an input image;
• a measuring step of measuring occurrence frequency of output color data of the lookup table;
• and
• a rewriting step of rewriting the lookup table based on a measured result from the measuring means such that dispersion of the measured occurrence frequency of each color is made smaller.

A display control apparatus for outputting a color image on the basis of color display data stored in a display memory, comprising:

• reading means for reading out the color display data from said display memory;
• palette means for inputting the color display data read out from said reading means and color converting;
• and
• output means for outputting the color display data which was color converted by said palette means,
• wherein said palette means has a rewritable lookup table for converting input colors, measuring means for measuring occurrence frequencies of output color data of said lookup table, data obtaining means for obtaining table data which makes a dispersion of the occurrence frequencies of said output color data lie within a predetermined range on the basis of the occurrence frequency of each color which was measured by said measuring means, and writing means for writing said table data obtained by said data obtaining means into said lookup table,
• wherein said lookup table converts input colors into colors of a number smaller than the number of input colors and outputs, and
• wherein when the dispersion of the occurrence frequency of each color is equal to or larger than a predetermined value, said data obtaining means selects at least one of the color of a large occurrence frequency and the color of a small occurrence frequency and obtains table data such as to narrow an input width of said color of the large occurrence frequency and to widen an input width of said color of the small occurrence frequency.