A print control data generating apparatus includes: a print image generator that generates a first print image having a size not larger than that of a print paper as a print image in a marginless printing; a print image modification unit that generates outside print images provided outside of the first print image generated by the print image generator based on a periphery of the first print image, to generate a second print image having a size larger than that of the print paper; and a print control data generator that generates print control data used in print control of a printer based on the second print image.

An ink jet printing method and an ink jet printing apparatus are provided which minimize an area to be printed that overruns from edge portions of the print medium, even for an irregular-shaped print medium. The printing apparatus has an overrunning ink reception opening formed in the platen as a notched portion to accommodate ink ejected beyond the edges of the print medium. When the edge portions of an irregular-shaped print medium are to be printed, a control is made to accommodate almost all volume of ink ejected beyond the edge portions in the overrunning ink reception opening. With this arrangement the amount of ink ejected from the edge portions of even the irregular-shaped print medium can be adjusted so that the interior of the platen and printing apparatus can be prevented from being contaminated and a wasteful ink consumption minimized, thus realizing a satisfactory "marginless printing."