CN103561252A - Method for color space conversion from HSL to RGB - Google Patents

Abstract

The invention discloses a method for color space conversion from HSL to RGB. The method includes the steps that standardization is carried out on the HSL, and the scope ranges from 0 to 240; if S equals to zero, the R, G and B are equal, fixed-point calculation standardization is carried out, and the scope of the RGB ranges from 0 to 255; if the S is not equal to zero, fixed-point calculation is carried out on p, q and hk; fixed-point initialization is carried out on t R, t G and t B; the fixed-point calculation is carried out on tc corresponding to each color; the corresponding colors are calculated according to the tc, the p and the q; standardization is carried out on the RGB, and the scope of the RGB ranges from 0 to 255. The method has the advantages that fixed-pointed processing is adopted, the method can be used in embedded 8-bit, 16-bit and 32-bit single-chip microcomputer systems and X86 systems, so the application scope is broadened greatly; some applications can be achieved on the single-chip microcomputers, so the system cost is reduced greatly; in addition, the efficiency of the floating point arithmetic mode is also improved.

Description

A kind of HSL is to the method for rgb color space conversion

Technical field

The present invention relates to video and technical field of image processing, particularly a kind of HSL is to the method for rgb color space conversion.

Background technology

RGB(RGB) be the space that the definitions of color according to eye recognition goes out, can represent most of color, it is the most general color model towards hardware.But in scientific research, generally do not adopt RGB color space, because its details is difficult to carry out digitized adjustment; In addition, it is difficult to the expression of putting together of three amounts of hue, saturation, intensity separately.

HSL color mode is a kind of color standard of industrial quarters, by variation and their stacks each other of tone (H), saturation (S), three Color Channels of brightness (L) are obtained to color miscellaneous, HSL is the color that represents tone, saturation, three passages of brightness, this standard almost comprised mankind eyesights can perception all colours, be to use at present one of the widest color system.

RGB is applicable to machine sampling, and current display color consists of these three kinds of primary colours; And HSL is applicable to video, image is processed and section's research.It is particularly necessary that succinct conversion between them seems.

Current common HSL to RGB conversion method is: a color of (h, s, l) value definition in given HSL space, with h the codomain of indication form and aspect angle [0,360) in, represent that respectively the s of saturation and brightness and l are in codomain [0,1] in, corresponding (r, g, b) three primary colors in RGB space, with corresponding respectively to redness, green and blue r, g and b are also in codomain [0,1], and they can be calculated as:

First, if s=0, the color of result is achromatic or grey.In these special circumstances, r, g and b equal l.The value of noting h is undefined in this case.

In the time of s ≠ 0, can use following process:

q=

p=

=

=

=

=

If <0

=

+1.0 for each C

{R,G,B}

If >1 =

-1.0 for each C

{R,G,B}

For each color vector color=(

,

) =( r, g, b)

=

for each C

{R,G,B}

In realizing process of the present invention, inventor finds that above-mentioned prior art exists following technical problem:

Be when in prior art, HSL is converted to rgb space, the poor compatibility of application; In addition, floating-point operation mode efficiency is low.

Summary of the invention

The object of this invention is to provide a kind of HSL to the method for rgb color space conversion, to realize the object that application is compatible good, floating-point operation mode efficiency is high.

For achieving the above object, the present invention is achieved through the following technical solutions:

HSL, to a method for rgb color space conversion, comprises the following steps:

1) HSL is demarcated, scope is between 0～240;

2) if S=0, RGB equates so, fixed-point computation is demarcated, RGB scope is between 0～255;

3) if S ≠ 0, so fixed-point computation p, q, hk; Fixed point initialization tR, tG, tB; The tc that each color of fixed-point computation is corresponding; According to tc, p, q, calculate corresponding color; Demarcate RGB, RGB scope is between 0～255.

Especially, described step 2), RGB calculating scaling method is: R=G=B=L*255/240.

Especially, in described step 3), q fixed-point computation method is: q=(l<120) ((unsigned short) (l * (240+s))/240): (l+s-(unsigned short) (l*s)/240).

Especially, in described step 3), p fixed-point computation method is: (2.0 * l) – q.

A kind of HSL of the present invention to the beneficial effect of the method for rgb color space conversion is: the present invention adopts fixed-point processing, can, for embedded 8,16,32 bit single-chip systems, also can, for X86 system, greatly expand range of application; For some application, can on single-chip microcomputer, realize, greatly lowered system cost; In addition, also improved floating-point operation mode efficiency.

Accompanying drawing explanation

Fig. 1 is that HSL of the present invention is to the flow chart of the method for rgb color space conversion.

Embodiment

To adopt 8 chip microcontroller color spaces to be converted to example, as shown in Figure 1, comprise the following steps:

1) HSL is demarcated, scope is between 0～240;

2) if S=0, RGB equates so, fixed-point computation is demarcated, RGB scope is between 0～255;

3) if S ≠ 0, so fixed-point computation p, q, hk; Fixed point initialization tR, tG, tB; The tc that each color of fixed-point computation is corresponding; According to tc, p, q, calculate corresponding color; Demarcate RGB, RGB scope is between 0～255.

Detailed process is as follows:

void hsl2rgb(u8 h,u8 s,u8 l,u8 *r,u8 *g,u8 *b)

{

unsigned short R, G, B;

unsigned char i;

if(s == 0)

{

R = G = B = l*255/240;

}

else

{

unsigned char q = (l<120) ((unsigned short)(l * (240+s))/240):(l+s -(unsigned short)(l*s)/240);

unsigned char p = (2.0 * l) - q;

unsigned char Hk = h;

unsigned short T[3];

T[0] = Hk + 80;

T[1] = Hk;

T[2] = Hk - 80;

for( i=0; i<3; i++)

{

if(T[i] < 0) T[i] += 240;

if(T[i] > 240) T[i] -= 240;

if((T[i]*6) < 240)

{

T[i] = p + ((q-p)*6*T[i])/240;

}

else if((T[i]*2) < 240)

{

T[i] = q;

}

else if((T[i]*3) < 480)

{

T[i] = p + (q-p) * (160 - T[i]) * 6/240;

}

else T[i] = p;

}

R = T[0]*255/240;

G = T[1]*255/240;

B = T[2]*255/240;

}

*r = (unsigned char)((R>255) 255 : ((R<0) 0 : R));

*g = (unsigned char)((G>255) 255 : ((G<0) 0 : G));

*b = (unsigned char)((B>255) 255 : ((B<0) 0 : B));

}。

Claims (4)

1. HSL, to a method for rgb color space conversion, is characterized in that, comprises the following steps:

1) HSL is demarcated, scope is between 0～240;

2) if S=0, RGB equates so, fixed-point computation is demarcated, RGB scope is between 0～255;

3) if S ≠ 0, so fixed-point computation p, q, hk; Fixed point initialization tR, tG, tB; The tc that each color of fixed-point computation is corresponding; According to tc, p, q, calculate corresponding color; Demarcate RGB, RGB scope is between 0～255.

2. HSL as claimed in claim 1, to a method for rgb color space conversion, is characterized in that: described step 2), RGB calculating scaling method is: R=G=B=L*255/240.

3. HSL as claimed in claim 1, to a method for rgb color space conversion, is characterized in that: in described step 3), q fixed-point computation method is: q=(l<120) ((unsigned short) (l * (240+s))/240): (l+s-(unsigned short) (l*s)/240).

4. HSL as claimed in claim 1, to a method for rgb color space conversion, is characterized in that: in described step 3), p fixed-point computation method is: (2.0 * l) – q.

Images