* Copyright (c) 2014, ArrayFire
* All rights reserved.
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
#include <arrayfire.h>
#include <stdio.h>
#include <cstdlib>
using namespace af;
// Split a MxNx3 image into 3 separate channel matrices.
static void channel_split(array& rgb, array& outr, array& outg, array& outb) {
outr = rgb(span, span, 0);
outg = rgb(span, span, 1);
outb = rgb(span, span, 2);
// 5x5 sigma-3 gaussian blur weights
static const float h_gauss[] = {
0.0318f, 0.0375f, 0.0397f, 0.0375f, 0.0318f, 0.0375f, 0.0443f,
0.0469f, 0.0443f, 0.0375f, 0.0397f, 0.0469f, 0.0495f, 0.0469f,
0.0397f, 0.0375f, 0.0443f, 0.0469f, 0.0443f, 0.0375f, 0.0318f,
0.0375f, 0.0397f, 0.0375f, 0.0318f,
// 3x3 sobel weights
static const float h_sobel[] = {-2.0, -1.0, 0.0, -1.0, 0.0, 1.0, 0.0, 1.0, 2.0};
// Demonstrates various image manipulations.
static void img_test_demo() {
af::Window wnd("Image Demo");
// load convolution kernels
array gauss_k = array(5, 5, h_gauss);
array sobel_k = array(3, 3, h_sobel);
// load images
array img_gray = loadImage(ASSETS_DIR "/examples/images/trees_ctm.jpg",
false); // 1 channel grayscale [0-255]
array img_rgb =
loadImage(ASSETS_DIR "/examples/images/sunset_emp.jpg", true) /
255.f; // 3 channel RGB [0-1]
array rotatedImg = rotate(img_gray, Pi / 2, false) / 255.f;
// array thrs_img = (img_gray < 130.f).as(s32);
array thrs_img = (img_gray < 130.f).as(f32);
// rgb channels
array rr, gg, bb;
channel_split(img_rgb, rr, gg, bb);
// hsv channels
array hsv = colorSpace(img_rgb, AF_HSV, AF_RGB);
array hh, ss, vv;
channel_split(hsv, hh, ss, vv);
// image histogram equalization
array ihist = histogram(img_gray, 256, 0, 255);
array inorm = histEqual(img_gray, ihist) / 255.f;
array edge_det = abs(convolve(img_gray, sobel_k)) / 255.f;
array smt = convolve(img_gray, gauss_k) / 255.f;
while (!wnd.close()) {
wnd.grid(2, 4);
// image operations
wnd(0, 0).image(img_rgb, "Input Image");
wnd(1, 0).image(rotatedImg, "Rotate");
wnd(0, 1).image(ss, "Saturation");
wnd(1, 1).image(bb, "Blue Channel");
wnd(0, 2).image(smt, "Smoothing");
wnd(1, 2).image(thrs_img, "Binary Thresholding");
wnd(0, 3).image(inorm, "Histogram Equalization");
wnd(1, 3).image(edge_det, "Edge Detection");;
int main(int argc, char** argv) {
int device = argc > 1 ? atoi(argv[1]) : 0;
try {
printf("** ArrayFire Image Demo **\n\n");
} catch (af::exception& e) {
fprintf(stderr, "%s\n", e.what());
return 0;
Window object to render af::arrays.
Definition: graphics.h:37
An ArrayFire exception class.
Definition: exception.h:22
virtual const char * what() const
Returns an error message for the exception in a string format.
Definition: exception.h:46
@ f32
32-bit floating point values
Definition: defines.h:211
3-channel HSV
Definition: defines.h:342
3-channel RGB
Definition: defines.h:341
AFAPI array abs(const array &in)
C++ Interface for absolute value.
AFAPI void info()
AFAPI void setDevice(const int device)
Sets the current device.
AFAPI array colorSpace(const array &image, const CSpace to, const CSpace from)
C++ Interface wrapper for colorspace conversion.
AFAPI array histEqual(const array &in, const array &hist)
C++ Interface for histogram equalization.
AFAPI array histogram(const array &in, const unsigned nbins, const double minval, const double maxval)
C++ Interface for histogram.
AFAPI array loadImage(const char *filename, const bool is_color=false)
C++ Interface for loading an image.
static af::array array(af::dim4 idims, cl_mem buf, af::dtype type, bool retain=false)
Create an af::array object from an OpenCL cl_mem buffer.
Definition: opencl.h:327
AFAPI array convolve(const array &signal, const array &filter, const convMode mode=AF_CONV_DEFAULT, const convDomain domain=AF_CONV_AUTO)
C++ Interface for convolution any(one through three) dimensional signals.
AFAPI array rotate(const array &in, const float theta, const bool crop=true, const interpType method=AF_INTERP_NEAREST)
C++ Interface for rotating an image.
Definition: algorithm.h:15
AFAPI const double Pi
AFAPI seq span
A special value representing the entire axis of an af::array.