RGBToHLS

Converts an RGB image to the HLS color model.

Syntax

IppStatus ippiRGBToHLS_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize roiSize);

Supported values for mod:

8u_C3R	16u_C3R	16s_C3R	32f_C3R
8u_AC4R	16u_AC4R	16s_AC4R	32f_AC4R

Parameters

pSrc	Pointer to the source image ROI.
srcStep	Distance in bytes between starts of consecutive lines in the source image.
pDst	Pointer to the destination image ROI.
dstStep	Distance in bytes between starts of consecutive lines in the destination image.
roiSize	Size of the source and destination ROI in pixels.

Description

The function ippiRGBToHLS is declared in the ippcc.h file. It operates with ROI (see Regions of Interest in Intel IPP).

This function converts the R'B'G' image pSrc to the HLS image pDst. For function flavors operating on the floating point data, source RGB values must be in the range [0..1].

The conversion algorithm from RGB to HLS can be represented in pseudocode as follows:

// Lightness:
M1 = max(R,G,B); M2 = min(R,G,B); L = (M1+M2)/2
// Saturation:
if M1 = M2 then // achromatics case
    S = 0
    H = 0
else // chromatics case
    if L <= 0.5 then
         S = (M1-M2) / (M1+M2)
    else
         S = (M1-M2) / (2-M1-M2)
// Hue:
Cr = (M1-R) / (M1-M2)
Cg = (M1-G) / (M1-M2)
Cb = (M1-B) / (M1-M2)
if R = M2 then H = Cb - Cg
if G = M2 then H = 2 + Cr - Cb
if B = M2 then H = 4 + Cg - Cr
H = 60*H
if H < 0 then H = H + 360

For floating point function flavors, the computed H, L, S values are scaled to the range [0..1]. In case of integer function flavors, these values are scaled to the full range of the destination data type (Table “Image Data Types and Ranges”).

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error.
ippStsNullPtrErr	Indicates an error condition if pSrc or pDst is NULL.
ippStsSizeErr	Indicates an error condition if roiSize has a field with a zero or negative value.