https://wiki.hoku.emelibrary.org/
2026-11-11T01:22:21+00:00
https://wiki.hoku.emelibrary.org/
https://wiki.hoku.emelibrary.org/_media/wiki:logo.pngtext/html2026-11-06T08:33:02+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)example_3 - Remove Example 3 (kept locally in the Hoku folder)
https://wiki.hoku.emelibrary.org/examples:example_3?rev=1793953982&do=diff
text/html2026-11-06T08:33:01+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)examples - Remove Example 3 (Slope)
https://wiki.hoku.emelibrary.org/examples?rev=1793953981&do=diff
Examples
These worked examples put several modules together into a complete job, from start to finish. They are built from the workflows in the Hoku tutorial.
Example Level What you will do Example 1: Enhance Contrast, Display and Save an Image Basic Read an image, stretch its contrast, check it in Show, and save it as a TIFF, with an optional JPEG copy to sharetext/html2026-11-06T08:18:57+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)example_1 - Retitle to Enhance Contrast, Display and Save; split window step into 3a-3c; TIFF primary, JPEG optional; add other ways to stretch
https://wiki.hoku.emelibrary.org/examples:example_1?rev=1793953137&do=diff
Example 1: Enhance Contrast, Display and Save an Image
Level: Basic
Modules: ReadImage, Pack, Show, WriteImage
Goal
Multispectral images are often 16-bit or floating-point files that other programs cannot display well. This job stretches the contrast of an image, converts it to 8 bits, displays it in Show so that you can check it, and saves it as a lossless TIFF file. You can also save a JPEG copy to share.text/html2026-11-05T18:44:26+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)flowchart_modules - if tests the file named in its exists entry (not only the current folder); link to Conditional Flowcharts
https://wiki.hoku.emelibrary.org/intermediate_level:flowcharts:flowchart_modules?rev=1793904266&do=diff
Flowchart Modules
The flowchart modules pass messages to each other, rather than images. Each message carries a directory (folder) name and a file name. This page lists what each module does. For how they work together, see Operation of Flowchart Modules.
Module What it does Argumenttext/html2026-11-05T18:44:13+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)conditional_flowcharts - Explain the if module's exists argument (expanded like exec, then tested), with a worked example, from the module code
https://wiki.hoku.emelibrary.org/advanced_level:conditional_flowcharts?rev=1793904253&do=diff
Conditional Flowcharts – if, yes, no
The Advanced level adds three flowchart modules that let a flowchart run its job only when a file exists, or only when it does not. They work with the Intermediate flowchart modules; see Batch Processing with Flowcharts.
Module What it doestext/html2026-11-05T18:44:13+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)display_window - Add the History, Bands and Pixelated/Smooth buttons (from the Show window code)
https://wiki.hoku.emelibrary.org/basic_level:show:display_window?rev=1793904253&do=diff
Show – The Display Window
Show creates a window in which its input image is displayed. This page describes the controls in that window.
[An image displayed in Show]
Window title
Each window is named “Image N-title”. N counts the images displayed so far, and the title is the one set in the Show arguments (text/html2026-11-05T18:43:51+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)power - Add the exact formulas for each operation and the shadows/highlights curves (from the module code)
https://wiki.hoku.emelibrary.org/intermediate_level:power?rev=1793904231&do=diff
Power
Power applies one of six non-linear operations to each pixel of the input image. In the formulas, x is the pixel value and “max” is the operation's constant for that band.
Operation Output power xa, with a constant power “a” (default 1.0)text/html2026-11-05T18:43:50+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)trc - Default command, the 12 colors and the hex mask, from the Show panel and TRC code
https://wiki.hoku.emelibrary.org/intermediate_level:trc?rev=1793904230&do=diff
TRC
TRC (tone reproduction) applies color adjustments that you made in Show to an image, so that you can apply the same adjustments in a job.
* Display an 8-bit color image in Show, and adjust it with the panel at the bottom of the window. See Show – The Display Window.text/html2026-11-05T18:43:50+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)imagemath - enhance applies to mod: arctan(factor x (mod - offset)); atan2 has no enhancement (from the module code)
https://wiki.hoku.emelibrary.org/intermediate_level:imagemath?rev=1793904230&do=diff
ImageMath
[ImageMath dividing one image by another]
ImageMath combines two images mathematically: an “input” image and an “op” (operation) image. In this example, the links show that the image on the left of ImageMath is the input image and the image on top is the op image. The operation istext/html2026-11-05T18:43:50+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)pattern - Add the random check box (from the module code)
https://wiki.hoku.emelibrary.org/advanced_level:pattern?rev=1793904230&do=diff
Pattern
Pattern generates a test image of a given size. It has no input. Patterns include random values, a constant gray level or color, and a wedge.
Argument What it does size Required. The “width” and “height” of the output, in pixels. One number gives a square imagetext/html2026-11-05T18:43:49+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)flatten - One dark value is used for both images (from the module code)
https://wiki.hoku.emelibrary.org/advanced_level:flatten?rev=1793904229&do=diff
Flatten
Flatten divides an image by its corresponding “flat” image (flat fielding), which corrects for uneven illumination. Connect the image to input_link and the flat image to flat_link.
Before the division, a dark value is subtracted from each image. Enter thetext/html2026-11-05T18:43:49+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)pseudocolor - Describe the blueorange scheme (UV red, average green, visible blue), from the module code
https://wiki.hoku.emelibrary.org/advanced_level:pseudocolor?rev=1793904229&do=diff
Pseudocolor
Pseudocolor combines two images of the same page into one color image: one taken under ultraviolet (UV) light, and one under visible (red) light. Connect them to ultraviolet_link and visible_link. Both must be single-band images of the same size.text/html2026-11-05T18:43:49+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)combine - Add output type (same data type and bits as inputs), from the module code
https://wiki.hoku.emelibrary.org/intermediate_level:combine?rev=1793904229&do=diff
Combine
Combine makes one color image from three monochrome images. In its arguments, choose which side of the module each image arrives on: red_link, green_link and blue_link.
The three images must each have one band, and must all have the same number of pixels and scanlines, the same number of bits, and the same data type. The output is a 3-band color image with the same data type and number of bits as the inputs.text/html2026-11-05T18:43:14+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)algorithms_available_in_cupboard - Add BandRatios (3.2) to the Spectral Analysis list
https://wiki.hoku.emelibrary.org/intermediate_level:algorithms_available_in_cupboard?rev=1793904194&do=diff
Intermediate Level – Algorithms Available in Cupboard
[The Cupboard at the Intermediate level]
The Intermediate level introduces new modules that enhance the ability to extract, enhance and display low-contrast information, while keeping all of the modules from the Basic level.
It also introduces a set of geometrically shaped modules at the beginning of the Cupboard. These are the elements of a flowchart, which you combine to run a job on a set of images, or on a set of folders.text/html2026-11-05T18:43:14+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)advanced_level - Update module count (39 Basic and Intermediate modules, with BandRatios)
https://wiki.hoku.emelibrary.org/advanced_level?rev=1793904194&do=diff
Advanced Level
The Advanced level shows every module: all 39 Basic and Intermediate modules, plus 21 more for image calibration, image analysis, flat fielding and registration, and conditional flowcharts. To switch to this level, see Changing Hoku Level.
New modulestext/html2026-11-05T18:43:13+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)intermediate_level - Add BandRatios (3.2) and update module counts
https://wiki.hoku.emelibrary.org/intermediate_level?rev=1793904193&do=diff
Intermediate Level
The Intermediate level keeps all 14 Basic modules and adds 25 more: 17 image-processing modules that extract, enhance and display low-contrast information, and 8 flowchart modules that run a job on many images or folders in batch. To switch to this level, seetext/html2026-11-05T18:43:13+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)hoku_levels - Add BandRatios (3.2, Intermediate) and update counts; note that plugins declare their own level (from the module code)
https://wiki.hoku.emelibrary.org/introduction:hoku_levels?rev=1793904193&do=diff
Hoku Levels
Hoku has three levels: Basic, Intermediate, and Advanced. The level controls which modules appear in the Cupboard. Each level keeps every module from the level below it and adds new ones, so the Advanced level shows all of them.
Basic is the default level.text/html2026-11-05T18:43:13+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)bandratios - New page for BandRatios (Hoku 3.2, Intermediate level per its algorithmLevel), from the module help
https://wiki.hoku.emelibrary.org/intermediate_level:bandratios?rev=1793904193&do=diff
BandRatios
BandRatios (Hoku 3.2) takes the ratio of every band of a multiband image with every band that follows it. Ratios with the bands before it would be redundant, so an image with N bands gives N(N−1)/2 output bands.
Order of the output bandstext/html2026-11-05T18:31:55+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)input - Add acknowledgment to MegaVision
https://wiki.hoku.emelibrary.org/intermediate_level:accucolor:input?rev=1793903515&do=diff
AccuColor – Input
In “input” mode, AccuColor converts a multiband image into a calibrated color image. For an overview of all modes, see AccuColor.
Paste the calibration matrix from “chart” mode (see Chart) into the “calibration” box. Then you can read all the images from the same imaging session into AccuColor, and it generates an 8-bit calibrated color image from each.text/html2026-11-05T18:31:55+00:00damian_hokuwiki (damian_hokuwiki@undisclosed.example.com)chart - Add acknowledgment to MegaVision
https://wiki.hoku.emelibrary.org/intermediate_level:accucolor:chart?rev=1793903515&do=diff
AccuColor – Chart
The “chart” mode has one input: a multiband image of the whole color checker chart, with all 24 patches visible. For an overview of all modes, see AccuColor.
[Input multiband image of the color chart]
Input multiband image of the color chart.
[AccuColor in chart mode]
[Output map showing where the patches were measured]
Output map showing where the patch measurements were made.