LBitmap::ColorThreshold

#include "ltwrappr.h"

virtual L_INT LBitmap::ColorThreshold (uColorSpace, pCompData, uFlags = 0)

L_UINT uColorSpace;

/* color space */

pCOMPDATA pCompData;

/* pointer to an array of structures */

L_UINT32 uFlags;

/* flags */

Using any one of eight color spaces, resets those bitmaps pixel component values that fall inside or outside of a specified range.

Parameter

Description

uColorSpace

Color space which the threshold is based on. Possible values are:

 

Value

Meaning

 

CLTH_RGB_SPACE

[0x00000000] RGB color space

 

CLTH_HSV_SPACE

[0x00000001] HSV color space

 

CLTH_HLS_SPACE

[0x00000002] HLS color space

 

CLTH_XYZ_SPACE

[0x00000003] XYZ color space

 

CLTH_YCrCb_SPACE

[0x00000004] YCrCb color space

 

CLTH_YUV_SPACE

[0x00000005] YUV color space

 

CLTH_LAB_SPACE

[0x00000006] LAB color space

 

CLTH_CMY_SPACE

[0x00000007] CMY color space

pCompData

Pointer to an array of 3 COMPDATA structures that contains the parameters used to compare and modify each component.

uFlags

Reserved for future use. Must be 0.

Returns

SUCCESS

The function was successful.

< 1

An error occurred. Refer to Return Codes.

Comments

This function is similar to the LBuffer::ConvertColorSpace function but provides greater flexibility by allowing the specification of a range and different options for handling those values that fall outside of the range. Please note that every color space component may have a different range.

Color Component

Range for 8-bit components

Range for 16-bit components

RGB

 

 

R

0 255

0 - 65535

G

0 255

0 - 65535

B

0 255

0 - 65535

HSV

 

 

H

0 - 360

0 - 36000

S

0 - 100

0 - 10000

V

0 - 255

0 - 65535

HLS

 

 

H

0 - 360

0 - 36000

L

0 - 255

0 - 65535

S

0 - 100

0 - 10000

XYZ

 

 

X

0 - 255

0 - 65535

Y

0 - 255

0 - 65535

Z

0 - 255

0 - 65535

YCrCb

 

 

Y

0 - 255

0 - 65535

Cr

-128 - 127

-32768 - 32767

Cb

-128 - 127

-32768 - 32767

YUV

 

 

Y

0 - 255

0 - 65535

U

-112 - 111

-28567 - 28566

V

-138 - 137

-35337 - 35336

LAB

 

 

L

0 - 100

0 - 10000

A

-128 - 127

-32768 - 32767

B

-128 - 127

-32768 - 32767

CMY

 

 

C

0 - 255

0 - 65535

M

0 - 255

0 - 65535

Y

0 - 255

0 - 65535

This function works as follows:

1.

The bitmap is converted to the required color space.

2.

For every pixel, the following operations are performed: Each component is compared with the nMinRange and nMaxRange ranges of the appropriate COMPDATA structure.

 

a.

If it is inside the range, the component is considered to have "passed" the test.

 

b.

.If it is outside the range, the component has been rejected". The CLTH_TYP_BANDREJECT flag inverts this by making "rejected" components "passed" and viceversa.

3.

If CLTH_MOD_CHANNEL is set, the components are modified independently. If CLTH_MOD_ALL has been passed, the pixel is rejected by the test if any component is rejected. If the pixel/component is rejected, then:

 

a.

If CLTH_VALUE_MIN is passed, the rejected pixel/component is set to 0.

 

b.

If CLTH_VALUE_MAX is passed, the rejected pixel/component is set to 255.

 

c.

If CLTH_VALUE_CLAMP is passed, components less that nMin go to 0 and components greater than nMax go to 255. This would work only with the CLTH_MOD_CHANNEL and CLTH_TYP_BANDPASS flag.

This function works for 1, 2, 3, 8,16, 24, 32, 48 and 64-bit color bitmaps and can support regions for 24 and 48-bit bitmaps. If a 24 or 48-bit bitmap has a region the effect will be applied on the region only.

One structure is used for each color component. The order is considered to be the same as in the CLTH_xxx_SPACE name. For example, for CLTH_RGB_SPACE:

pCompData[0] structure is used for the Blue component

pCompData[1] structure is used for the Green component

pCompData[2] structure is used for the Red component

The pCompData[0].uStructSize must be set to sizeof(COMPDATA) before calling this function. For an array of structures, only the first structure in the array needs to have uStructSize member set.

To update a status bar or detect a user interrupt during execution of this function, refer to LBase::EnableStatusCallback.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Required DLLs and Libraries

LTIMGCLR

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

See Also

Functions:

LBitmap::AdjustTint. LBitmap::ColorHalfTone, LBitmap::BinaryFilter, LBuffer::ConvertColorSpace, LBitmap::ColorSeparate, LBitmap::ColorMerge, LBitmap::AddShadow, LBitmap::AllocFTArray, LBitmap::ChangeHueSatInt, LBitmap::ColorReplace, LBitmap::DFT, LBitmap::DirectionEdgeStatistical, LBitmap::FFT, LBitmap::FreeFTArray, LBitmap::FrqFilter, LBitmap::FrqFilterMask, LBitmap::FTDisplay, LBitmap::GetStatisticsInfo, LBitmap::GetFeretsDiameter, LBitmap::GetObjectInfo, LBitmap::GetRgnContourPoints, LBitmap::GetRgnPerimeterLength, LBitmap::MathFunction, LBitmap::RevEffect, LBitmap::Segment, LBitmap::SubtractBackground, LBitmap::UserFilter, LBitmap::DirectionEdgeStatistical2

Topics:

Correcting Colors

 

Raster Image Functions: Modifying Intensity Values

 

Raster Image Functions: Getting and Setting Pixel Values

 

Raster Image Functions: Doing Color Space Conversions

 

Raster Image Functions: Correcting Colors

Example

L_INT LBitmap__ColorThresholdExample(LBitmap *pLeadBitmap) 
{
   COMPDATA          pCompData[3]; 
   L_INT                     nI; 
   pCompData[0].uStructSize = sizeof(COMPDATA); 
   for (nI = 0; nI < 3; nI++)
   {
       pCompData[nI].nMinRange = 128; 
       pCompData[nI].nMaxRange = 255; 
       pCompData[nI].uFlags = 0; 
   }
   /* Apply color Threshold effect on the image*/
   return pLeadBitmap->ColorThreshold(CLTH_RGB_SPACE,  pCompData); 
}