1. Field of the Invention
The present invention relates to an image processing apparatus, and image processing method and a memory medium.
2. Related Background Art
Conventionally there is known a color copying apparatus capable of printing bit map data representing characters or patterns, outputted from a computer or the like.
In such color copying apparatus, the general resolving power (resolution) for a character is currently 400 dip (dot/inch), so that the dots are printed with a pitch of 63.5 xcexcm. On the other hand, there is being proposed a technology of printing a character with 800 dpi in order to increase the resolving power.
On the other hand, in case of printing a character or a fine line utilizing the color copying apparatus as a printer, there are contained various densities. Therefore, even if a character or a line image is detected by pattern matching and the detected edge of the character or line is uniformly interpolated with the doubled resolving power and with the multi-value density in order to cancel the jagged appearance generated by rasterizing on such edge, the reproducibility in the low density range is insufficient for the lines of a high resolving power because of the characteristics of the printer.
More specifically, in case the image data of a low density area are dispersed into fine plural pixels by interpolation and are printed with the doubled resolving power, there may result drawbacks such as the printed area being invisible or a blurred edge because the pixels are small and of a low density.
Also the output characteristics of the printer are different for the printing with 400 dpi and that with 800 dpi.
Also the linearity between the input density and the output density may be degraded by the change with the lapse of time.
FIG. 11 is a chart showing the relationship between the input density and the output density at different resolving powers of 400 and 800 dpi.
Comparison of 400 and 800 dpi in FIG. 11 indicates that the resolution of 400 dpi is closer to the ideal density characteristics in almost all the density levels.
In consideration of the foregoing, it is not desirable to increase the resolving power depending on the density of the image.
In consideration of the foregoing, an object of the present invention is to provide an image processing apparatus, an image processing method and a memory medium therefor, allowing to effect image formation with optimum resolving power and density according to the density of the image data.
Another object of the present invention is to provide an image processing apparatus, an image processing method and a memory medium therefor capable, in case of forming a color image based on color image data input from an external device, of smoothing the contour of the printed character or pattern and also selecting the optimum resolving power and density according to the output density thereby improving the print quality.
The above-mentioned objects can be attained, according to a preferred embodiment of the present invention, by an image processing apparatus-comprising:
an input unit for inputting image data;
a judging unit for judging whether the image data represent a line image area;
a conversion unit for converting the resolving power by executing an interpolation process to the image data;
comparing means for comparing the image data, obtained by the conversion unit, with a specific density; and
control means for selecting whether to record the image data with a first resolving power or with a second resolving power higher than the second resolving power, according to a result obtained by the judging unit and a result obtained by the comparing unit.
Still another object of the present invention is to provide an image processing apparatus, an image processing method and a memory medium therefor, provided with a novel function.