ppmtoleaf

Convert a PPM image to a LEAF file

$ ppmtoleaf [path/to/file.ppm] > [path/to/file.leaf]

`ppmtoleaf [-width width] [-height height] [-threshold | -diffusion | -clusters | -dots] [-gamma gamma] [-x x] [-y y] [-yoffset yoffset] [-yincr yincr] [-reverse] [ppmfile]`

-width width
    Specifies the desired output width in pixels. If omitted, the width is inherited from the input image.

-height height
    Specifies the desired output height in pixels. If omitted, the height is inherited from the input image.

-threshold
    Uses a simple thresholding algorithm for halftoning, converting pixels directly to black or white based on a cutoff value.

-diffusion
    Employs an error diffusion halftoning algorithm (e.g., Floyd-Steinberg), which spreads quantization errors to neighboring pixels, often resulting in a more uniform appearance.

-clusters
    Applies a clustered-dot halftoning method, where dots are grouped together to create darker shades. This is common for traditional printing.

-dots
    Uses a dispersed-dot halftoning method, distributing dots more evenly across the image to simulate shades, which can appear finer but might be more sensitive to printing errors.

-gamma gamma
    Applies a gamma correction factor to the image before halftoning, adjusting the tonal curve to compensate for display or printing characteristics.

-x x
    Sets the starting X coordinate for the output image within the Leaf file's internal coordinate system.

-y y
    Sets the starting Y coordinate for the output image within the Leaf file's internal coordinate system.

-yoffset yoffset
    Specifies a vertical offset for interleaved output, useful when generating multiple strips of an image.

-yincr yincr
    Defines the vertical increment for interleaved output, used in conjunction with -yoffset for multi-strip image generation.

-reverse
    Inverts the monochrome output image (black becomes white and vice-versa).

ppmfile
    The input `Portable Pixmap` (`PPM`) image file. If not specified, `ppmtoleaf` reads `PPM` data from standard input (stdin).

`ppmtoleaf` is a Netpbm program that reads a `Portable Pixmap` (`PPM`) image as input and produces a `Leaf Technologies` (`Leaf`) image as output. The `Leaf` format was originally developed by Leaf Technologies, which was later acquired by Mitsubishi Electric Research Labs (MERL), for use in their high-quality digital halftone printing systems. This command is particularly useful for workflows that require generating images compatible with `Leaf`'s proprietary imaging hardware or software.

It handles the pixel data conversion, ensuring the output is correctly structured for the `Leaf` format. As the `Leaf` format is often a 1-bit monochrome format, `ppmtoleaf` typically performs a halftoning or dithering process on the input `PPM` to simulate shades of gray or color using varying dot patterns. It provides several algorithms for this conversion, allowing users to choose the best method for their specific printing or display requirements. While `Leaf` is a specialized format, `ppmtoleaf` serves as a crucial bridge for integrating standard Netpbm image processing into such specific systems. It's part of a larger suite of Netpbm utilities designed to convert between various image formats, promoting interoperability within diverse imaging pipelines.

The `Leaf` format is a specialized, proprietary image format primarily associated with older high-end printing systems by Leaf Technologies and Mitsubishi Electric Research Labs (MERL). It is not a broadly supported or commonly used image format in general modern image processing workflows.

The halftoning options (-threshold, -diffusion, -clusters, -dots) are mutually exclusive; only one can be chosen per invocation.

Input must be a valid `Portable Pixmap` (`PPM`) file. `ppmtoleaf` does not convert other image formats directly; use other Netpbm tools to convert to `PPM` first if necessary.

When converting a full-color or grayscale `PPM` to a 1-bit `Leaf` image, ppmtoleaf employs halftoning. This process simulates continuous tones by varying the density and pattern of binary dots. The choice of halftoning algorithm (e.g., error diffusion, clustered dots) significantly impacts the visual quality and detail preservation of the monochrome output, especially for high-resolution printing.

The `Leaf` format is typically a raster image format often used for high-resolution monochrome output. It was designed for specific professional imaging devices, particularly digital proofing and computer-to-plate systems. Its usage is niche and specific to workflows involving Leaf Technologies or MERL hardware and software. For general image viewing or editing, conversion to more common formats like `PPM` or `PNG` is usually necessary.

ppmtoleaf is a component of the Netpbm project, which traces its roots back to Jef Poskanzer's Pbmplus toolkit, initially developed in the late 1980s. Netpbm evolved into a comprehensive, open-source suite for graphics file format conversions and image manipulation. This command specifically extended Netpbm's capabilities to support the proprietary `Leaf Technologies` image format, facilitating interoperability between standard image formats and specialized printing systems prevalent at the time.

ppm(5), netpbm(1), pnmtoleaf(1), leaftoppm(1), leafinfo(1), pnmdither(1), pgmtoleaf(1)