topic Converting float matrix to rgb in Intel® Integrated Performance Primitives

Converting float matrix to rgb

John_M_3 — Fri, 14 Jul 2017 13:13:49 GMT

I have the following code written to have IPP resize my matrix:

#include "ipp_mx.h"
#include "ipp.h"

#include "stdafx.h"
#define IPPCALL(name) name

int main()
{
    IppiSize srcSize = { 3,3 };
    float srcImage[9] =
    { 20, 40, 30,
      35, 55, 70,
      100, 30, 20 };
    float* src = new float[srcSize.width*srcSize.height];
    for (int i = 0; i < srcSize.width*srcSize.height; i++) {
        src = srcImage;
    }
    double xFactor = 10; double yFactor = 10;

    int numChannels = 1;
    int bytesPerPixel = 4;
    int srcStep = srcSize.width*bytesPerPixel*numChannels;
    IppiRect srcRoi = { 0, 0, srcSize.width, srcSize.width };

    float* dest = new float[srcSize.width*srcSize.height*xFactor*yFactor];
    IppiSize destSize = { srcSize.width*xFactor, srcSize.height*yFactor };
    int destStep = destSize.width*bytesPerPixel*numChannels;
    IppiRect destRoi = { 0, 0, destSize.width, destSize.width };

    double xShift = 0; double yShift = 0;

    int interpolation = 1; //nearest neighbour

    int bufSize;
    IPPCALL(ippiResizeGetBufSize)(srcRoi, destRoi, 1, interpolation, &bufSize);
    unsigned char* buffer = new unsigned char[bufSize];

    IPPCALL(ippiResizeSqrPixel_32f_C1R)(src, srcSize, srcStep, srcRoi, dest, destStep, destRoi, xFactor, yFactor, xShift, yShift, interpolation, buffer);
    return 0;
}

Is there an IPP function I can use that now converts this float matrix dest to an RGB24 format, given a colour map?

I know I can do it by hand in a for loop, but the raw matrices I want to work with are much larger and for loops may not cut it.

Hi,

Chao_Y_Intel — Mon, 31 Jul 2017 02:53:33 GMT

Hi,
Can you suggest how do you want to perform the conversion? Intel IPP provides one mapping function here:
https://software.intel.com/en-us/node/504062
Can this function be used there?
If the code just want to convert some data types, it can use the ippiConvert functions:
https://software.intel.com/en-us/node/503746

regards,
Chao

Hi,

John_M_3 — Mon, 31 Jul 2017 13:19:00 GMT

Hi,

How I wanted to perform the conversion was, given a float value and an array that maps value ranges to RGB colours, convert the float value to an RGB colour.

What I ended up doing was:

ippiConvert_32f8u_C1R - convert the float image to char by truncating as in my case I don't need the decimal precision as the colour steps are integer.
ippiGrayToRGB_8u_C1C3R - convert the float to RGB.
ippiLUTPallete_8uC3R - given a palette, transform the gray values into colour.

Say a pixel value is 20.5.

ippiConvert_328u_C1R converts it to 20.
ippiGrayToRGB_8u_C1C3R converts the pixel to 3 channels of 20 red, 20 green, 20 blue.
Construct a palette that maps 20 red, 20 green, 20 blue to, say, 0 red, 0 green, 255 blue.
Pass the RGB converted pixel and the pallet to ippiLUTPallete_8uC3R which makes the proper transformation to 0, 0, 255.

Thank you