Beeldpatches

Beeldpatches, or image patches, are small, usually square regions extracted from a larger image to serve as basic units for analysis and processing. They capture local structure and texture and allow algorithms to operate on a manageable, localized representation rather than the entire image at once. Patches can be grayscale or color and are commonly arranged with overlaps, depending on the task.

Extraction and representation

Patches are typically obtained by sliding a window of fixed size across the image. Common patch sizes range from 8x8 to 32x32 pixels, though larger or smaller sizes are used for specific applications. Each patch can be treated as a feature vector or as a small image block that supports local descriptors (such as color, texture, gradients) or learned representations through dictionary learning and sparse coding. In modern deep learning, patches may be processed as inputs to networks or used for data augmentation, although many architectures operate on full images.

Applications and methods

Beeldpatches are central to many image processing tasks. In denoising, patch-based methods compare similar patches across the image to reconstruct clean pixels, exemplified by non-local means and BM3D. In texture synthesis and image quilting, patches from a source texture are stitched to generate larger images. Patch-based matching underpins stereo vision, image inpainting, and super-resolution, with algorithms like PatchMatch providing fast approximate nearest-neighbor search for patch correspondences. Dictionary learning approaches (e.g., K-SVD) model images as patches drawn from a sparse representation over a learned dictionary.

Limitations and considerations

Challenges include computational cost from processing many patches and boundary handling when tiling patches. Overlapping patches require careful aggregation, often by averaging or weighted fusion, to avoid seams. Patch-based methods have been complemented by deep learning, where networks learn patch-level features as part of larger end-to-end models.

Note

The term beeldpatches is Dutch for image patches; in English-language literature, "image patches" or "patches" is typically used.