The Maximum Level component scans through all pixels of the original image currently loaded into Filter Forge (see Image component) and extracts its maximum grayscale level or maximum R, G and B levels. The alpha channel of the source image is ignored. This component, together with the Minimum Level component, can be used to build automatic tonal range adjustments, for example a Levels operation that automatically adjusts its black and white points. Maximum Level is a map component, it can be located in the External category on the Components Bar. Note that this component works on the external image only and cannot use other components as sources.
Any filter that includes the Maximum Level component is automatically classed as an Effect Filter. For more information, see Filter Classes.
Cutoff: Map Input
Adjusts the component's sensitivity to noise. A non-zero Cutoff prevents high-brightness noise or occasional bright pixels from affecting the resulting maximum level. This parameter has the range of 0 to 50 and specifies the maximum percentage of the image area that can be disregarded during the calculation. That is, a Cutoff of 5 basically 'tells' the component that 'when calculating the maximum level, you can exclude the brightest pixels from the calculation, but make sure that the number of such pixels does not exceed 5% of the image's total number of pixels'.
Cutoff is a map input, so you can control the sensitivity separately for different image areas by connecting a map component to this input. However, this is not necessary in the majority of cases.
When Mode is set to Gray Level, the component extracts the maximum grayscale level of the source image. In a simple case when Cutoff is 0, this is the grayscale level of the brightest pixel of the image. With a non-zero Cutoff, the component excludes high-brightness noise or occasional bright pixels from the calculation. The grayscale level of a pixel is calculated by averaging its R, G and B channels (the alpha channel is ignored).
When Mode is set to RGB Levels, the algorithm is basically the same, but instead of a single grayscale level, the component extracts the maximum levels of R, G and B channels separately. The extracted levels are then combined into a single color to form the result. Since the levels are extracted separately, the resulting color produced by the component may not match any of the actual pixels of the original image (that is, the maximum R level may be taken from one pixel, the maximum G level from another one, etc.). The resulting combined color has little practical value, so you may want to use the Extract RGB component to separate the combined R, G and B levels.
When a map component is connected to this input, the number of the selected list item is determined separately for different image areas by the HDR brightness level of the image supplied by that component. The item number is calculated as the brightness level rounded to the nearest integer: brightness levels below 0.5 correspond to the first item, while levels of 0.5 and above correspond to the second item.
