Intel® Integrated Performance Primitives
Deliberate problems developing high-performance vision, signal, security, and storage applications.

Converting float matrix to rgb


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.

0 Kudos
2 Replies

Can you suggest how do you want to perform the conversion?   Intel IPP provides one mapping function here:
Can this function be used there? 
If the code just want to convert some data types, it can use the  ippiConvert functions:


0 Kudos


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:

  1. 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.
  2. ippiGrayToRGB_8u_C1C3R - convert the float to RGB.
  3. ippiLUTPallete_8uC3R - given a palette, transform the gray values into colour.

Say a pixel value is 20.5.

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

Thank you 


0 Kudos