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3 Texture Synthesis for Natural Images
Based on the image quilting algorithm, our idea is to utilize a target image which
has the same size as the desired output image and contains the layout information as
the input. In the IQ algorithm, the error surface of searching for the best match patch
is calculated in the region of the overlap, which has the size of 40 x 10 pixels in our
implementation. For the sake of the layout information, we simply upscale the input
image to be the same size as the output image, and use it as the target image for
controlling the synthesis process.
In the original IQ algorithm, only the overlap region as indicated in Fig. 1 is used
to find good matches in the input texture. Since we want our new algorithm to be
constrained by the target image, the match window is a whole block consisting of
the overlap region from the completed portion and the remaining region from the
target image, as illustrated in Fig. 3. The synthesis process starts with the target
image as the initialization of the output. For the first patch in the top-left corner, the
match window in the output image contains all the pixels from the target image,
because no completed portion is available yet. Similar as IQ, a specified error
tolerance is set to find several good matches from which a randomly selected patch
is copied into the corresponding location in the output. Minimum error boundary
cut is also adopted on the overlap regions to make the transitions between patches
smooth. Fig. 4 depicts an example of finding of the minimum error boundary cuts.
The process for finding good matches from the input texture is repeated until all the
pixels in the output image are updated.
(a) Input image
(b) Target image
(c) Zoom-in synthesis process
Fig. 4 Illustration of updating patches in the proposed algorithm. From left to right shows (a)
the input image, (b) the target image and (c) a zoom-in synthesis process of the top-left part
of (b), and the white curves illustrate the found minimum error boundary cuts.
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