IMcHistogram2LuminanceLimits Property

Property Value

Type: Object

By default, the histogram consists of bins covering the source McImage.RangeMin to RangeMax. If the actual luminance values in the source image cover only a small fraction of the RangeMin to RangeMax, this default behavior may lead to all pixel counts falling into one or two histogram bins, losing all measure of the actual spread of pixel luminance values. The effect is especially severe for 32-bit integral pixels, where each of 64K histogram bins will by default cover a luminance range of 64K units. Similar issues can easily arise with floating point pixels when RangeMin to RangeMax need to be set conservatively to encompass the results of multiplicative computations. To address this situation, the mchmHonorLuminanceLimits Mode property bit may be set, in which case the histogram is computed over the LuminanceLimits property's start to end range. If the mchmAutoSetLuminanceLimits Mode bit is set, then the LuminanceLimits are automatically set to the absolute range of luminance values found in the source image whenever Compute is called. The LuminanceLimits can be set by calling the ComputeLuminanceLimits method or by assigning to the property. Assigning to the LuminanceLimits will automatically clear the mchmAutoSetLuminanceLimits Mode bit. The LuminanceLimits property is exposed as a DOUBLERANGE value. On assignment, it may be assigned from a DOUBLERANGE, LONGRANGE or any length-2 numeric array. It is legal to assign value outside of an ancestor image's RangeMin to RangeMax, though this rarely makes sense. It is illegal to assign start and end values that are out-of-order. For integral source image types, if the difference between the LuminanceLimits end and start is less than the BinCount-1, then the number of bins in the histogram is decreased so that the BinLuminanceWidth is one luminance value. The LimitedBinCount property will reflect this shortened histogram length, if it is necessary; otherwise LimitedBinCount will equal BinCount.