A Method to Generate Hybrid Pointillistic Images
Junichi Sugita*
Tokyo Healthcare University

Tokiichiro Takahashi*Tokyo Denki University / UEI Research

Figure 1: Example of hybrid pointillistic images.

1 Introduction
A hybrid image is an image that changes interpretation as a functionof viewing distance [Oliva et al. 2006]. Hybrid image IH obtainedby superimposing two images, I1 and I2, is represented as follows:= ( ) + ( ),(1)where Lp is a low-pass filter and Hp is a high-pass filter. The lowpass filtered blurred image is seen by viewers at a far distance, andthe high-pass filtered sharp image is seen by viewers closer to thedisplay.
In this study, we propose a method to generate hybrid pointillistic
images that are non-photorealistic style hybrid images (see Fig. 1).
Hybrid pointillistic images are generated by superimposing two
non-photorealistic images; one is pointillistic for far viewers, andthe other is stippled for near viewers.

at a close distance. To prevent viewers who are near fromperceiving an image that is meant to be perceived from far away,
applying an error-diffusion method works well.
2.2 Generating stippled images for near-distance viewing
We generated a stippled image for near-distance viewing. First, weapplied a high-pass filter to the input image to generate a highfrequency (HF) map. Next, an error-diffusion method was applied
to the HF map. We adopted a structure-preserving stippling (SPS)
method for error-diffusion, because an SPS method can express thestructure of the input image and control the density of dots byaltering several parameters. When stippling is directly generated
from an input image, the desired change of perception of the two
images based on distance does not occur.

2 Proposed Method
To change the perception of the images according to viewing
distance, blurred and sharp images are required. The blurred andsharp images are obtained by altering the sizes of the dots that makeup the images. Thus, using large dots creates a pointillistic blurred
image, and using small dots creates a stippled sharp image.
Figure 2 shows the flow of our hybrid pointillistic image generation
method. Hybrid pointillistic image IHP is generated from two input
images, I1 and I2, which is expressed as follows:= ( )+( ( )),(2)where PH is created using a pointillisitic halftoning method [Sugitaand Takahashi 2013], and SPS is created using a structurepreserving stippling method [Li and Mould 2011].
2.1 Generating pointillistic images for far-distance viewing
We generated a pointillistic image for far-distance viewing using apointillistic halftoning (PH) method. PH is a method for applying
an error-diffusion algorithm to random sampling dots to achieve apointillistic appearance. Pointillistic images with large dots appearas a blurred image, such as a mosaic image. A problem with hybrid
images is that the blurred images can still be perceived by viewers* e-mail: {sugita, toki}@vcl.jp

Permission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor commercial advantage and that copies bear this notice and the full citation on thefirst page. Copyrights for third-party components of this work must be honored. For allother uses, contact the Owner/Author.
Copyright is held by the owner/author(s).
SA’15 Posters, November 02 – 06, 2015, Kobe, Japan.
ACM 978-1-4503-3926-1/15/11.
http://dx.doi.org/10.1145/2820926.2820962

Figure 2: Hybrid pointillistic image generation.

3 Results
Figure 1 shows the hybrid pointillistic image that we generated.
The original size of the image was 1024 × 957 pixels. The radiusof dots used to create the pointillistic image was 14 pixels, and theradius of the dots used for stippling was 1 pixel. When viewed fromup close, an owl is perceived from a stippled image. When theviewer steps a meter away, he or she sees a lion depicted in apointillistic image. Instead of having the viewer step away, we cansimulate that action by downscaling the image gradually. Suddenly,
at a certain distance (or size of the image), the perception of theimage is changed.

References
OLIVA, A., TORRALBA A., AND SCHYNS, P. G. 2006. Hybrid Images.
ACM Transactions on Graphics, 25, 3 (July), 527–532.
SUGITA, J., AND TAKAHASHI, T. 2013. A Method for Generating
Pointillism Based on Seurat’s Color Theory, ITE Transactions
on Media Technology and Applications, 1, 4 (Oct), 317–327.
LI, H., AND MOULD, D. 2011. Structure-preserving Stippling by
Priority-based Error Diffusion. In Proc. of GI 2011, 127–134.