Bicubic interpolation

About: Bicubic interpolation is a research topic. Over the lifetime, 3348 publications have been published within this topic receiving 73126 citations.

Invisible seams

Abstract: Surface materials are commonly described by attributes stored in textures (for instance, color, normal, or displacement). Interpolation during texture lookup provides a continuous value field everywhere on the surface, except at the chart boundaries where visible discontinuities appear. We propose a solution to make these seams invisible, while still outputting a standard texture atlas. Our method relies on recent advances in quad remeshing using global parameterization to produce a set of texture coordinates aligning texel grids across chart boundaries. This property makes it possible to ensure that the interpolated value fields on both sides of a chart boundary precisely match, making all seams invisible. However, this requirement on the uv coordinates needs to be complemented by a set of constraints on the colors stored in the texels. We propose an algorithm solving for all the necessary constraints between texel values, including through different magnification modes (nearest, bilinear, biquadratic and bicubic), and across facets using different texture resolutions. In the typical case of bilinear magnification and uniform resolution, none of the texels appearing on the surface are constrained. Our approach also ensures perfect continuity across several MIP-mapping levels.

Improved rhombus interpolation for reversible watermarking by difference expansion

Abstract: The paper proposes an interpolation error expansion reversible watermarking algorithm. The main novelty of the paper is a modified rhombus interpolation scheme. The four horizontal and vertical neighbors are considered and, depending on their values, the interpolated pixel is computed as the average of the horizontal pixels, of the vertical pixels or of the entire set of four pixels. Experimental results are provided. The proposed scheme outperforms the results obtained by using the average on the four horizontal and vertical neighbors and the ones obtained by using well known predictors as MED or GAP.

Comparison of projection algorithms used for the construction of maximum intensity projection images.

Abstract: Four methods of producing maximum intensity projection (MIP) images were studied and compared. Three of the projection methods differ in the interpolation kernel used for ray tracing. The interpolation kernels include nearest neighbor interpolation, linear interpolation, and cubic convolution interpolation. The fourth projection method is a voxel projection method that is not explicitly a ray-tracing technique. The four algorithms` performance was evaluated using a computer-generated model of a vessel and using real MR angiography data. The evaluation centered around how well an algorithm transferred an object`s width to the projection plane. The voxel projection algorithm does not suffer from artifacts associated with the nearest neighbor algorithm. Also, a speed-up in the calculation of the projection is seen with the voxel projection method. Linear interpolation dramatically improves the transfer of width information from the 3D MRA data set over both nearest neighbor and voxel projection methods. Even though the cubic convolution interpolation kernel is theoretically superior to the linear kernel, it did not project widths more accurately than linear interpolation. A possible advantage to the nearest neighbor interpolation is that the size of small vessels tends to be exaggerated in the projection plane, thereby increasing their visibility. The results confirm thatmore » the way in which an MIP image is constructed has a dramatic effect on information contained in the projection. The construction method must be chosen with the knowledge that the clinical information in the 2D projections in general will be different from that contained in the original 3D data volume. 27 refs., 16 figs., 2 tabs.« less

Theoretical development for pointwise digital image correlation

Abstract: The theoretical foundation is developed for a new technique to determine displacements with subpixel accuracy at each pixel location in a digital image of a deformed object using digital image correlation (DIC). This technique, known as pointwise DIC, is evaluated using ideal sinusoidal images for the cases of rigid body translation, extensional strain, and rigid body rotation. Displacement fields obtained using objective correlation functions with and without intensity gradients are compared. Both bilinear and bicubic interpolation schemes are investigated for reconstructing the subpixel intensity and intensity gradient values in undeformed and deformed images. The effects of transforming the Eulerian description of the intensity gradients in the deformed images to the Lagrangian description in the undeformed images are also investigated. The optimal correlation value and the calculated displacement fields of the two interpolation schemes are compared. Theoretical results demonstrate that pointwise DIC can accurately determine displacement fields. To demonstrate the advantages of pointwise DIC over conventional DIC techniques, an ideal image simulating a twinning deformation is correlated, indicating the pointwise technique is up to two orders of magnitude more accurate at determining discontinuous displacements than the conventional technique. Experiments are also conducted on a polycarbonate dogbone specimen that validate pointwise DIC on real images and determine the inherent accuracy in the digital image acquisition.