Imaging toolbox

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imaging-2014.png

This toolbox controls how the post-processed result image buffer is displayed on screen. It also affects how low dynamic range image formats (JPEG and PNG) are saved.

Channel

The image channel to display may be selected here. If your image has R, G and B channels, the "RGB" option is also available, and generates a color image.

Example

By default, instruments have X, Y and Z observers defined according to the CIE 1931 colorimetric system. Ocean generates an image buffer with X, Y and Z channels. Then, a postprocessing filter named xyztorgb converts these channels to R, G and B channels.

Drawing a chart of scene luminance requires the Y channel. First disable the xyztorgb filter in the postprocessing settings. Also disable the smartclamp filter, which can only work in RGB space. The available choices in the channel list box will change to X, Y and Z. Select Y, you now have an image representing the scene luminance in grey scale.

Curve control

The Cornell Box imaged in sRGB

This option affects how the selected channel(s) are mapped to pixel values.

Linear

The channel value is mapped linearly. A channel value of 0 is mapped to 0, and a buffer value of 1.0 is mapped to 255.

sRGB

The channel value is mapped according to the sRGB standard curve. Use this option for generating images. This is roughly equivalent to a gamma of 2.2, but not exactly.

Gamma

The channel value is mapped by a power function : f(x)=255*x^(1/gamma).

Log

The channel value is mapped by a base 10 logarithm function. The resulting logarithm is then mapped to 0-255 by an affine function : log10(1.0)=0.0 is mapped to 255, and log10(10^-decads)=-decads is mapped to 0.


Coloring

The Cornell Box imaged in Y luminance, with a logarithmic thermal color scale

When a single channel is selected (not RGB), this controls how the value is displayed in a color image.

Greyscale

The value is mapped to a level of grey.

Hue

The value is mapped to a rainbow hue gradient.

Thermal

The value is mapped to a thermal imaging like color gradient.

Overlay information

This adds some rendering information and statistics at the bottom left of the image.