Scale

Scales pixel values of an image and converts them to another bit depth.

Syntax

Case 1: Scaling with conversion to integer data of increased bit depth

IppStatus ippiScale_<mod>(const Ipp<srcDatatype>* pSrc, int srcStep, Ipp<dstDatatype>* pDst, int dstStep, IppiSize roiSize);

Supported values for mod:

8u16u_C1R	8u16s_C1R	8u32s_C1R
8u16u_C3R	8u16s_C3R	8u32s_C3R
8u16u_C4R	8u16s_C4R	8u32s_C4R
8u16u_AC4R	8u16s_AC4R	8u32s_AC4R

Case 2: Scaling with conversion to floating-point data

IppStatus ippiScale_<mod>(const Ipp8u* pSrc, int srcStep, Ipp32f* pDst, int dstStep, IppiSize roiSize, Ippi32f vMin, Ippi32f vMax);

Supported values for mod:

8u32f_C1R

8u32f_C3R

8u32f_C4R

8u32f_AC4R

Case 3: Scaling of integer data with conversion to reduced bit depth

IppStatus ippiScale_<mod> (const Ipp<srcDatatype>* pSrc, int srcStep, Ipp<dstDatatype>* pDst, int dstStep, IppiSize roiSize, IppHintAlgorithm hint);

Supported values for mod:

16u8u_C1R	16s8u_C1R	32s8u_C1R
16u8u_C3R	16s8u_C3R	32s8u_C3R
16u8u_C4R	16s8u_C4R	32s8u_C4R
16u8u_AC4R	16s8u_AC4R	32s8u_AC4R

Case 4: Scaling of floating-point data with conversion to integer data type

IppStatus ippiScale_<mod>(const Ipp32f* pSrc, int srcStep, Ipp8u* pDst, int dstStep, IppiSize roiSize, Ippi32f vMin, Ippi32f vMax);

Supported values for mod:

32f8u_C1R

32f8u_C3R

32f8u_C4R

32f8u_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.
vMin, vMax	Minimum and maximum values of the input data.
hint	Option to select the algorithmic implementation of the function.

Description

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

This function converts pixel values of a source image ROI pSrc to the destination data type, using a linear mapping. The computation algorithm is specified by the hint argument (see Table Hint Arguments for Image Moment Functions). For conversion between integer data types, the whole range [src_Min..src_Max] of the input data type is mapped onto the range [dst_Min..dst_Max] of the output data type (see Intel® Integrated Performance Primitives Concepts for more information on data types and ranges).

The following scaling formula to map the source pixel p to the destination pixel p′ is used:

p′ = dst_Min + k*(p - src_Min)

where k = (dst_Max - dst_Min)/(src_Max - src_Min).

For conversions to and from floating-point data type, the user-defined floating-point data range [vMin..vMax] is mapped onto the source or destination data type range.

If the conversion is from Ipp32f type and some of the input floating-point values are outside the specified input data range [vMin..vMax], the corresponding output values will saturate. To determine the actual floating-point data range in your image, use the function ippiMinMax.

Example “Data Conversion with Scaling” shows how to use scaling to preserve the data range.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr	Indicates an error when any of the specified pointers is NULL.
ippStsSizeErr	Indicates an error condition if roiSize has a field with a zero or negative value.
ippStsStepErr	Indicates an error condition if srcStep or dstStep has a zero or negative value.
ippStsScaleRangeErr	Indicates an error condition if the input data bounds are incorrect, that is, vMax is less than or equal to vMin .

Data Conversion with Scaling

IppStatus scale( void ) { IppiSize roi = {5,4}; Ipp32f x[5*4]; Ipp8u y[5*4]; ippiSet_32f_C1R( -1.0f, x, 5*sizeof(Ipp32f), roi ); x[1] = 300; x[2] = 150; return ippiScale_32f8u_C1R( x, 5*sizeof(Ipp32f), y, 5, roi, -1, 300 ); }

The destination image y contains:
00 FF 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00