man pages section 3: Multimedia Library Functions
Updated: July 2014

## mlib_ImageColorHSL2RGB (3MLIB)

### Name

mlib_ImageColorHSL2RGB - HSL to RGB color conversion

### Synopsis

```cc [ flag... ] file... –lmlib [ library... ]
#include <mlib.h>

mlib_status mlib_ImageColorHSL2RGB(mlib_image *dst, const mlib_image *src);```

### Description

The mlib_ImageColorHSL2RGB() function performs a conversion from hue/saturation/lightness to red/green/blue. The source and destination images must be three-channel images.

It uses the following equations:

```   L' = L          if L ≤ 1/2
L' = 1 - L      if L > 1/2

V = L + S*L'
P = L - S*L'
Q = L + S*L'*(1 - 2*fraction(H*6))
T = L - S*L'*(1 - 2*fraction(H*6))

R, G, B = V, T, P    if 0   ≤ H < 1/6
R, G, B = Q, V, P    if 1/6 ≤ H < 2/6
R, G, B = P, V, T    if 2/6 ≤ H < 3/6
R, G, B = P, Q, V    if 3/6 ≤ H < 4/6
R, G, B = T, P, V    if 4/6 ≤ H < 5/6
R, G, B = V, P, Q    if 5/6 ≤ H < 1
```

where 0 ≤ H < 1 and 0 ≤ S, L, L', V, P, Q, T, R, G, B ≤ 1.

Assuming a pixel in the source image is (h, s, l) and its corresponding pixel in the destination image is (r, g, b), then for MLIB_BYTE images, the following applies:

```   H = h/256
S = s/255
L = l/255
r = R*255
g = G*255
b = B*255
```

for MLIB_SHORT images, the following applies:

```   H = (h + 32768)/65536
S = (s + 32768)/65535
L = (l + 32768)/65535
r = R*65535 - 32768
g = G*65535 - 32768
b = B*65535 - 32768
```

for MLIB_USHORT images, the following applies:

```   H = h/65536
S = s/65535
L = l/65535
r = R*65535
g = G*65535
b = B*65535
```

and for MLIB_INT images, the following applies:

```   H = (h + 2147483648)/4294967296
S = (s + 2147483648)/4294967295
L = (l + 2147483648)/4294967295
r = R*4294967295 - 2147483648
g = G*4294967295 - 2147483648
b = B*4294967295 - 2147483648
```

### Parameters

The function takes the following arguments:

dst

Pointer to destination image.

src

Pointer to source image.

### Return Values

The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.

### Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
MT-Safe