We present a technique to print physical prototypes
with the main characteristics
of watercolors
using a photograph as input.
Our prints combine
fine details
& subtle color gradients
& exhibit delicate patterns
created by water.
We achieve reproducibility by
printing with woodblocks.
In woodblock printing the
negative of a single colored
image is carved on a flat
wood surface.
Ink is applied on it
before is pressed on a paper.
The woodblocks are designed by
our image processing pipeline
and carved by a laser-cutter.
A photograph with
the desired theme
is given as input.
We use a color palette
extraction algorithm
based on K-means
to output the “color map”.
The color “color map”
assigns pixels
to a set of watercolor paints
with the same size
and appearance
as the color palette.
A multiclass image
segmentation algorithm
based on a probabilistic
graphical model
maps the pixels to a set
of user proposed semantic
classes and outputs the
“semantic map”.
Next a defocus estimation
algorithm outputs
the "smoothness map”.
The darker the color value
the sharper the photograph
is on that pixel.
We combine
the “semantic map”
the “smoothness map”
and the designer given threshold
to get the “water map” image.
White and black represent areas
that watercolors and drycolors
are applied respectively.
The user selects the
area of interest.
First we print the
masking fluid
a rubber material that
controls the water application.
For the design of the
masking fluid woodblock
we combine the dry color area,
edges extracted by the
Canny edge detector
and the user selected area.
We use an aerosol spray
to dampen the paper
following the same sequence
of sprayings and absorptions
for all of our results.
Next, we print the watercolors.
For the design of the
watercolor woodblocks
we expand every color of the
water color area
taking into account the
masking fluid area
and the details.
This step creates overlapping
blocks one for every color
which allows to design smooth
gradients between them.
To fabricate the shading blocks
we proposed a novel approach
that identifies and expands
local extrema
on an image.
Please look the paper
for details.
The local minima define
a woodblock with a
a darker shade of color.
While the local maxima are
areas that we subtract
from the watercolor woodblocks.
The local minima and maxima
create the shading.
Finally we print the dry
colors and the details.
To design the drycolor
woodblocks, we intersect
the “Color map” with the
dry color area.
To design the detail woodblocks
we extract finer minima
and combine them with edges
of the dry color area.
The last spray facilitates
the colors to diffuse.
please look into the
supplemental material
for details our choices on
the fabrication pipeline.
Here you see prints
with different colors
or printed differently
the interpretation of these
results is up to the designers'
aesthetics.
We selected heterogeneous
photographs to see if our
pipeline generalizes well.
A portrait highlights
the shading on the 3D
geometry of the face.
The flower shows the smoothness
of the color diffusion between
two different colors.
While the bird extends it
to more than two.
In contrast to previous results
this image has more detailed
texture
on the dry color area.