Three-dimensional image forming system and three-dimensional structure

1. A three-dimensional image forming system comprising:

a processor configured to adjust, for print data for printing a grayscale image used to cause a predetermined region of a thermally expandable sheet to thermally expand, a density of the grayscale image according to types of pattern images included in the grayscale image, in print regions of the pattern images such that expansion heights of the print regions of the pattern images become desired heights,

wherein the processor defines the density of the grayscale image corresponding to the expansion height and an area of the print regions of the pattern images, for each type of the pattern images included in the grayscale image, and

wherein the processor is configured to, in a case where a plurality of the print regions included in the grayscale image are overlapped with each other, adjust the density of an overlapping region in which the plurality of the print regions are overlapped with each other to be zero.

2. The three-dimensional image forming system according to claim 1 , wherein the processor adjusts the density of the grayscale image in a print region of a closed curve included in the grayscale image and a print region of a pattern image arranged inside the closed curve.

3. The three-dimensional image forming system according to claim 1 , wherein the print data comprises bitmap data.

4. The three-dimensional image forming system according to claim 1 , wherein the pattern images include at least one of a stripe pattern and a dot pattern.

5. The three-dimensional image forming system according to claim 4 , wherein the pattern images include at least one of stripe patterns and dot patterns having different sizes.

6. The three-dimensional image forming system according to claim 1 , wherein the processor is configured to:

generate synthesized print data by synthesizing mask data, in which the density is zero, with the print data at the overlapping region in the grayscale image to be printed onto a surface of the thermally expandable sheet; and

cause a printer to print the grayscale image based on the synthesized print data.

7. The three-dimensional image forming system according to claim 6 , wherein the surface is a surface of a base material which is a component of the thermally expandable sheet.

8. The three-dimensional image forming system according to claim 6 , wherein the surface is a surface of a thermal expansion layer which is a component of the thermally expandable sheet.

9. A three-dimensional image forming method comprising:

adjusting, for print data for printing a grayscale image used to cause a predetermined region of a thermally expandable sheet to thermally expand, a density of the grayscale image according to types of pattern images included in the grayscale image, in print regions of the pattern images such that expansion heights of the print regions of the pattern images become desired heights,

wherein the adjusting comprises defining the density of the grayscale image corresponding to the expansion height and an area of the print regions of the pattern images, for each type of the pattern images included in the grayscale image, and

wherein the adjusting comprises, in a case where a plurality of the print regions included in the grayscale image are overlapped with each other, adjusting the density of an overlapping region in which the plurality of the print regions are overlapped with each other to be zero.

10. A non-transitory computer-readable storage medium having a program stored thereon, the program being executable by a processor of a three-dimensional image forming system to control the processor to perform processes comprising:

adjusting, for print data for printing a grayscale image used to cause a predetermined region of a thermally expandable sheet to thermally expand, a density of the grayscale image according to types of pattern images included in the grayscale image, in print regions of the pattern images such that expansion heights of the print regions of the pattern images become desired heights,

wherein the adjusting comprises defining the density of the grayscale image corresponding to the expansion height and an area of the print regions of the pattern images, for each type of the pattern images included in the grayscale image, and

wherein the adjusting comprises, in a case where a plurality of the print regions included in the grayscale image are overlapped with each other, adjusting the density of an overlapping region in which the plurality of the print regions are overlapped with each other to be zero.