图像自适应的曲边多边形网格生成
Image-Adaptive Generation of Polygonal Meshes with Curved Edges
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摘要: 将图像抽象成几何表示是图像处理领域的一类重要问题.为了提升多边形网格捕捉图像弯曲特征的能力,进一步增强重建图像的质量,提出一种图像自适应的曲边多边形网格的变分生成方法.首先将定义在网格上的分片逼近函数到输入图像的距离作为能量函数,并求解其最小值产生图像自适应的多边形网格;然后引入二次Bézier曲线弯曲网格的每条边,提升网格捕捉图像特征的能力;为了高效地优化网格,推导出能量函数关于网格顶点与Bézier控制点的显式梯度公式,并基于超像素构造初始网格后采用交替优化策略对两者进行迭代更新.与现有的曲边三角形网格或普通多边形网格等方式进行对比的实验结果表明,所提方法在图像逼近质量与视觉效果方面均有显著的提升,所得重建图像与原图像的均方根误差与曲边三角形网格相比普遍降低3.57%~6.97%,与普通多边形网格相比普遍降低39.81%~56.94%.Abstract: Abstracting images into geometric representations is an important topic in the field of image processing. To improve the ability of polygonal meshes in capturing curved features of images and further enhance the quality of reconstructed images, this paper proposes a variational generation framework for polygonal meshes, which sets the distance between piecewise approximating functions defined on the mesh and the input image as an energy function, and minimizes it to generate image-adaptive polygonal meshes. Quadratic Bézier curves are introduced to bend each mesh edge, thereby enhancing the mesh’s capability to capture image features. To efficiently optimize the mesh, explicit gradient formulas of the energy function with respect to mesh vertices and Bézier control points are derived, and an alternating optimization strategy is employed to iteratively update these two items after mesh initialization using superpixels. Compared with existing approaches such as curved triangular meshes or ordinary polygonal meshes, the results of our method demonstrate remarkable improvements in both image approximation quality and visual effects, the root mean square error between the reconstructed images and the original images is generally reduced by 3.57% to 6.97% compared to curved triangular meshes, and by 39.81% to 56.94% compared to ordinary polygon meshes.
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