Chroma Key TOP

From TouchDesigner 099 Wiki


Summary

The Chroma Key TOP pulls a key matte from the image using Hue, Saturation, and Value settings. If a pixel falls between the Min and Max parameters for all three settings, then it is included in the key. It outputs an alpha map, or the image with the key color removed.

See also the chromaKey component in the Palette, which is a user interface around the Chroma Key TOP that lets you grab frames on-the-fly and interactively set set the key color ranges. The UI also adds edge softening and color spill controls.

PythonIcon.png chromakeyTOP_Class

Parameters - Hue Page

Hue Min /huemin - The minimum hue value that is added to the chroma key. 0 = min, 360 = max.

Hue Max /huemax - The maximum hue value that is added to the key. 0 = min, 360 = max.

Hue Soft Low /hsoftlow - The rate of falloff at the Hue Min setting.

Hue Soft High /hsofthigh - The rate of falloff at the Hue Max setting.

Parameters - Sat Page

Sat Min /satmin - The minimum saturation value that is added to the key.

Sat Max /satmax - The maximum saturation value that is added to the key.

Sat Soft Low /ssoftlow - The rate of falloff at the Sat Min setting.

Sat Soft High /ssofthigh - The rate of falloff at the Sat Max setting.

Parameters - Val Page

Val Min /valmin - The minimum value that is added to the key.

Val Max /valmax - The maximum value that is added to the key.

Val Soft Low /vsoftlow - The rate off falloff at the Val Min setting.

Val Soft High /vsofthigh - The rate of falloff at the Val Max setting.

Parameters - Output Page

Invert New Alpha /invert - Inverts the key that is created.

RGB Output /rgbout - Determines the output of the RGB channels from the Chroma Key TOP.

  • Source RGB * New Alpha - Multiplies the original image with the key that is created. This has the effect of removing the parts of the image that are not included in the key.
  • New Alpha - Sets R, G, and B channels equal to the key that has been pulled.

Alpha Output /alphaout - Determines the output of the Alpha channel from the Chroma Key TOP.

  • New Alpha - Sets the Alpha ouput to be the key that has been pulled.
  • Source Alpha * New Alpha - Multiplies the original alpha channel with the new key that has been pulled.

Parameters - Common Page

Output Resolution - quickly change the resolution of the TOP's data.

  • Use Input - uses the input's resolution.
  • Eighth, Quarter, Half, 2X, 4X, 8X - multiply the input's resolution by that amount.
  • Fit Resolution - Resizes the input to the size specified in Resolution using the best possible match that does not crop any of the input. It will resize the image to be larger than the input resolution if a larger resolution is specified. It's a "fit inside", Aspect Ratio is maintained.
  • Limit Resolution - Limits the input to the size specified in Resolution using the best possible match that does not crop any of the input. It will NOT resize the image to be larger than the input resolution if a larger resolution is specified. It's a "fit inside", Aspect Ratio is maintained.
  • Custom Resolution - enables the Resolution parameter below, giving direct control over width and height.

Resolution - enabled only when the Resolution parameter is set to Custom Resolution. Some Generators like Constant and Ramp do not use inputs and only use this field to determine their size. The drop down menu on the right provides some commonly used resolutions.

Use Global Res Multiplier - Uses the Global Resolution Multiplier found in Edit>Preferences>TOPs. This multiplies all the TOPs resolutions by the set amount. This is handy when working on computers with different hardware specifications. If a project is designed on a desktop workstation with lots of graphics memory, a user on a laptop with only 64MB VRAM can set the Global Resolution Multiplier to a value of half or quarter so it runs at an acceptable speed. By checking this checkbox on, this TOP is affected by the global multiplier.

Output Aspect - sets the image aspect ratio allowing any textures to be viewed in any size. Watch for unexpected results when compositing TOPs with different aspect ratios. (You can define images with non-square pixels using xres, yres, aspectx, aspecty where xres/yres != aspectx/aspecty.)

  • Input - uses the input's aspect ratio.
  • Resolution - uses the aspect of the image's defined resolution (ie 512x256 would be 2:1), whereby each pixel is square.
  • Custom Aspect - lets you explicitly define a custom aspect ratio in the Aspect parameter below.

Aspect - Use when Output Aspect parameter is set to Custom Aspect.

Input Smoothness - This controls pixel filtering on the input image of the TOP.

  • Nearest Pixel - uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
  • Interpolate Pixels - uses linear filtering between pixels. This is how you get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
  • Mipmap Pixels - uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail.

Fill Viewer - determine how the TOP image is displayed in the viewer.

  • Input - uses the same Fill Viewer settings as it's input.
  • Fill - stretches the image to fit the edges of the viewer.
  • Fit Horizontal - stretches image to fit viewer horizontally.
  • Fit Vertical - stretches image to fit viewer vertically.
  • Fit Best - stretches or squashes image so no part of image is cropped.
  • Fit Outside - stretches or squashes image so image fills viewer while constraining it's proportions. This often leads to part of image getting cropped by viewer.
  • Native Resolution - displays the native resolution of the image in the viewer.

NOTE: To get an understanding of how TOPs works with images, you will want to set this to Native Resolution as you lay down TOPs when starting out. This will let you see what is actually happening without any automatic viewer resizing.

Viewer Smoothness - This controls pixel filtering in the viewers.

  • Nearest Pixel - uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
  • Interpolate Pixels - uses linear filtering between pixels. Use this to get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
  • Mipmap Pixels - uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail. When the input is 32-bit float format, only nearest filtering will be used (regardless of what is selected).

Passes - duplicates the operation of the TOP the specified number of times.

Channel Mask - Allows you to choose which channels (R, G, B, or A) the TOP will operate on. All channels are selected by default.

Pixel Format - format used to store data for each channel in the image (ie. R, G, B, and A). Refer to Pixel Formats for more information.

  • Input - uses the input's pixel format.
  • 8-bit fixed (RGBA) - uses 8-bit integer values for each channel.
  • sRGB 8-bit fixed (RGBA) - uses 8-bit integer values for each channel and stores color in sRGB colorspace.
  • 16-bit float (RGBA) - uses 16-bits per color channel, 64-bits per pixel.
  • 32-bit float (RGBA) - uses 32-bits per color channel, 128-bits per pixels.


  • 10-bit RGB, 2-bit Alpha, fixed (RGBA) - uses 10-bits per color channel and 2-bits for alpha, 32-bits total per pixel.
  • 16-bit fixed (RGBA) - uses 16-bits per color channel, 64-bits total per pixel.
  • 11-bit float (RGB), Positive Values Only - A RGB floating point format that has 11 bits for the Red and Green channels, and 10-bits for the Blue Channel, 32-bits total per pixel (therefore the same memory usage as 8-bit RGBA). The Alpha channel in this format will always be 1. Values can go above one, but can't be negative. ie. the range is [0, infinite).
  • 8-bit fixed (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 8-bits per pixel.
  • 16-bit fixed (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
  • 16-bit float (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
  • 32-bit float (Mono) - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 32-bits per pixel.
  • 8-bit fixed (RG) - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 8-bits per channel, 16-bits total per pixel.
  • 16-bit fixed (RG) - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
  • 16-bit float (RG) - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
  • 32-bit float (RG) - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 32-bits per channel, 64-bits total per pixel.
  • 8-bit fixed (A) - An Alpha only format that has 8-bits per channel, 8-bits per pixel.
  • 16-bit fixed (A) - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
  • 16-bit float (A) - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
  • 32-bit float (A) - An Alpha only format that has 32-bits per channel, 32-bits per pixel.
  • 8-bit fixed (Mono+Alpha) - A 2 channel format, one value for RGB and one value for Alpha. 8-bits per channel, 16-bits per pixel.
  • 16-bit fixed (Mono+Alpha) - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
  • 16-bit float (Mono+Alpha) - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
  • 32-bit float (Mono+Alpha) - A 2 channel format, one value for RGB and one value for Alpha. 32-bits per channel, 64-bits per pixel.