posterize 2.10.0

Posterize an image with stacked SVG geometry (generated by Potrace).

Posterize

Posterize an image with stacked SVG geometry (generated by Potrace).

API

The package exposes four main functions and two result types:

• posterize(image_path, num_cols, *, savings_weight=None, vibrant_weight=None, max_dim=None) Load an image from disk and posterize it. Returns a Posterization. image_path: path to the image. num_cols: number of colors (layers) in the result; fewer may be returned if colors are exhausted. savings_weight: weight for sum savings vs average savings when choosing layer colors (default 0.25). vibrant_weight: bias toward more vibrant colors, 0–1 (default 0). max_dim: if set, resize the image so its longer side is at most this many pixels before processing.

• posterize_mono(pixels, num_cols, *, savings_weight=None, vibrant_weight=None) Posterize a grayscale pixel array. Returns a Posterization. pixels: (r, c) uint8 array (e.g. one channel of an image). num_cols, savings_weight, vibrant_weight: same as posterize.

• new_target_image(path, max_dim=None) Quantize an image file to at most 512 colors and return a TargetImage (palette, indices, cost matrix). Used internally by posterize; useful if you need the quantized image without building layers. path: path to an image file. max_dim: maximum width or height; image is thumbnailed if larger (default 500).

• new_target_image_mono(pixels) Quantize a grayscale (r, c) uint8 array to at most 256 colors. Returns a TargetImage. Used internally by posterize_mono.

Result types: Posterization (from posterize / posterize_mono) has .write_svg(path, num_cols=None) and methods for layers, colors, and SVG elements. TargetImage holds the quantized palette, indices, and cost matrix for layer-building.

Example

from posterize import posterize

posterized = posterize("image.png", 4)
posterized.write_svg("output.svg")

Caching

• .cache_posterize (in the current working directory) Memoizes posterize() and posterize_mono() by their arguments. Repeated calls with the same inputs return the cached Posterization without recomputing layers.

• .cache_quantize (in the current working directory) Memoizes quantized image data: quantize_image() / quantize_rgba() and quantize_mono(). Used by new_target_image() and new_target_image_mono(), and indirectly by posterize() and posterize_mono().

• Temp directory (paths.CACHE_DIR, under the system temp dir as cluster_colors_cache) Used while generating SVG paths: a temporary BMP and Potrace-generated SVG are written here during layer_to_svgd() and then removed. No long-lived cache.