How to change dpi in PostScript -

i newcomer in postscript language. using ps print scaled image of dots. default dpi in ps 72dpi, wondering how change 600dpi.

the code write follows, square of dots.

%%dot_unit %%position setting 100 200 translate %%size setting     52 49 scale %%parameter setting:width height bit matrix 52 49 1 [52 0 0 -49 0 49] %%dot unit discribe {< fff7ff7ff7ff7f  ffffffffffffff ffffffffffffff ffffffffffffff fffff7ffff7fff ffffffffffffff ffffffffffffff ffffffffffffff ffffffffffffff fdfffffdffffff ffffffffffffff ffffffffffffff 7ff7ff7ff7ff7f ffffffffffffff ffffffffffffff ffffffffffffff ffff7ffffff7ff ffffffffffffff ffbfffffbfffff ffffffffffffff ffffffffffffff ffffffffffffff ffffffffffffff ffffffffffffff 7ff7ff7ff7ff7f ffffffffffffff ffffffffffffff ffffffffffffff fffffff7ffffff ffffffffffffff fffffbffffffff ffffffffffffff ff7fffffffffff ffffffffffdfff ffffffffffffff ffffffffffffff 7ff7ff7ff7ff7f ffffffffffffff ffffffffffffff ffffffffffffff ffffffff7fffff ffffffffffffff ffffffffffffff ffffffffffffff ff7fffffffffff 7fffdfffffdfff ffffffffffffff ffffffffffffff fff7ff7ff7ff7f >} image showpage 

there no default dpi in postscript. user space set co-ordinate system 72 units inch, that's not same thing. if want different user space alter ctm (current transformation matrix). co-ordinate system alterations rely on changes matrix, ctm.

in case of images, image operator maps image 1 unit square area, passed through image matrix render canvas, using ctm. in case of example above image scaled factor of 52 in x direction , 49 in y direction. if change scale or image matrix, different results.

the area covered image device-independent, when print user space objects rendered device space (using device matrix). if printer 600 dpi or 2400 dpi, image still cover same area on output page.

all need worry area want covered, don't need concerned resoltuion.