How to read a .tif floating point gray scale image in openCV - c++

Question

I am trying to read a .tif or .tiff floating point gray scale image in OpenCV.
I can read and write routine file format such as png, jpg etc but I am not able to read from my Desktop a format I never used before which is .tif or .tiff format.
The image: the image I am trying to read has the following parameters:
Size:
And width and height:
After some documentation and various sources I was able to understand that it is possible to use a convertTo function to convert between available data types, the source can be found here. However this didn't work well and I actually had a compilation error saying:
OpenCV(3.4.1) Error: Assertion failed (size.width>0 && size.height>0) in imshow, file /home/to/opencv/modules/highgui/src/window.cpp, line 356
terminate called after throwing an instance of cv::Exception
what(): OpenCV(3.4.1) /home/to/opencv/modules/highgui/src/window.cpp:356: error: (-215) size.width>0 && size.height>0 in function imshow
The code I am using is the following:
#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include <string>
using namespace cv;
using namespace std;
int main( int argc, char** argv )
{
Mat img = imread("/home/to/Desktop/example.tif");
cv::imshow("source",img);
Mat dst; // destination image
// check if we have RGB or grayscale image
if (img.channels() == 3) {
// convert 3-channel (RGB) 8-bit uchar image to 32 bit float
img.convertTo(dst, CV_32FC3);
}
else if (img.channels() == 1) {
// convert 1-chanel (grayscale) 8-bit uchar image to 32 bit float
img.convertTo(dst, CV_32FC1);
}
// display output, note that to display dst image correctly
// we have to divide each element of dst by 255 to keep
// the pixel values in the range [0,1].
cv::imshow("output",dst/255);
waitKey();
}
Additional example I tried to make it work is directly from the OpenCV documentation which can be found here, with a small modification though. I read from official documentation that the options IMREAD_ANYCOLOR | IMREAD_ANYDEPTH should also be activated and in fact is what I did in the second additional trial below:
#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include <string>
using namespace cv;
using namespace std;
int main( int argc, char** argv )
{
String imageName( "/home/to/Desktop/example.tif" ); // by default
if( argc > 1)
{
imageName = argv[1];
}
Mat image;
Mat outImage;
image = imread( imageName, IMREAD_ANYCOLOR | IMREAD_ANYDEPTH ); // Read the file
if( image.empty() ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
return -1;
}
namedWindow( "Display window", WINDOW_AUTOSIZE ); // Create a window for display.
resize(image, outImage, cv::Size(500,500));
imshow("orig", image);
imshow("resized", outImage);
// Show our image inside it.
waitKey(0); // Wait for a keystroke in the window
return 0;
This time the compiler runs without any error but no image is shown as it is possible to see from the print screen below:
UPDATE
This is the result after the cv::resize
UPDATE 2
This the result after applying imshow("Display window", image*10);
Is there something that I am missing from the official documentation or something else I am forgetting to do?
Thanks for shedding light on this issue.

Answer 1

Your image is composed of a single channel of 64-bit floats which range from -219.774 to -22.907. I can tell that using tiffutil which is shipped with libtiff:
tiffutil -verboseinfo image.tif
TIFFReadDirectory: Warning, Unknown field with tag 33550 (0x830e) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 33922 (0x8482) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
Directory at 0x256b3a2
Image Width: 2277 Image Length: 2153
Bits/Sample: 64
Sample Format: IEEE floating point
Compression Scheme: none
Photometric Interpretation: "min-is-black"
Samples/Pixel: 1
Rows/Strip: 1
Number of Strips: 2153
Strips (Offset, ByteCount):
17466, 18216
35682, 18216
53898, 18216
...
...
I am not certain exactly what you plan to do, but as a first stab, you can just add 220 to every pixel and convert to unsigned char and your range will be 0 to 197 which is perfectly displayable:
I actually did it using Python because I am quicker with that, but the C++ will follow exactly the same format:
import cv2
# Load image
img = cv2.imread('image.tif',cv2.IMREAD_UNCHANGED)
# Add 220 to all values, round to unsigned 8-bit and display
Image.fromarray((img+220).astype(np.uint8)).show()