I have a floating point data [size: 4000 X 140 ]. I want to convert it to an IplImage in OpenCV. To have an idea about data, I am giving first 8 X 8 entries of that data.These data are very close to zero. So, I am getting a dark image.
-1.14E-04 -4.71E-04 -1.27E-04 2.43E-04 4.58E-04 1.63E-04 2.56E-04 2.86E-04
1.12E-04 -2.80E-04 2.89E-05 -2.18E-04 4.08E-05 -2.23E-04 -7.96E-05 -3.97E-05
-3.98E-04 -2.35E-04 6.11E-04 4.53E-05 4.74E-05 8.02E-05 2.10E-04 1.10E-04
2.08E-04 3.09E-04 -1.34E-04 -2.58E-04 -2.25E-04 -1.74E-04 2.28E-04 2.65E-04
-6.65E-04 -2.94E-04 6.37E-04 -5.16E-05 9.90E-05 1.05E-04 -2.20E-04 -5.49E-05
1.85E-04 5.69E-04 -5.19E-04 -4.98E-05 2.07E-04 -2.00E-05 1.24E-04 1.49E-04
1.54E-04 -4.09E-04 4.29E-04 -7.67E-04 5.19E-04 3.56E-04 -4.82E-04 3.66E-04
-1.71E-04 -5.15E-04 5.71E-04 -5.68E-04 -2.75E-04 -6.17E-05 1.40E-04 2.19E-04
1) when I am multiplying these entries with a factor like 10E4 or 10E5, I can see an image. But image quality is very poor unlike matlab-generated image.
[
MATLAB code corresponding image:
[path,file] = uigetfile;
data = load(strcat(file,path));
figure;
imagesc(data);
colormap(gray);
]
[
OpenCV code sequence:
I created CvMat and filled it with those data.
I prepared IplImage from that CvMat.
I resized the image( 560 X 420 )
]
2) There are many negative data. Should those be consider zero? or Should all the data be added with a number(like 10E-4) to make all entries positive? or should I proceed through someother ways?
3) I changed contrast , brightness. But those seem to be useless.
Try mapping the minimum value to 0.0 and the maximum to 1.0.
Related
I have data that change in size and want to display them in the same window. The command
void ImageResize( BasicImage im, Number num_dim, Number... )
seems like a potential fit, but the syntax is not clear at all.
Let's say I have 512x5 data set and now it needs to be 367x5.
The , Number...) indicates that this command takes a different number of parameters, all of them interpreted as number parameters. Commands which do this, usually use one of their other parameters to specify how many such parameters follow.
A typical example for this is also the SliceN command.
In this particular case, the command not only allows you to change the size of the dimensions in the image, but also the number of dimensions. It is a very useful command to f.e. change a 2D image into a 3D stack or the like.
The command ImageResize( BasicImage im, Number num_dim, Number... ) does several things:
It replaces im in-place, so the meta-data, display and window remains the same
It adjusts the dimension calibration when the dimension size is changed. Here, the assumption is, that the field-of-view before and
after the resize is the same. (The command can be used to easily scale
images as shown in the example below.)
All values of the image im are set to zero. ( If you need to keep the values, you need to act on an image clone!)
Example 1: Resizing image with bilinar interpolation
image before := GetFrontImage()
number sx, sy
before.GetSize(sx,sy)
number factor = 1.3
image after := before.ImageClone()
after.ImageResize( 2, factor*sx, factor*sy ) // Adjusts the empty container with meta-data
after = warp(before, icol/factor, irow/factor ) // interpolate data
after.ShowImage()
Example 2: Extend 2D image into 3D stack
number sx = 100
number sy = 100
image img := RealImage("2D",4,sx,sy)
img = iradius* Random()
img.ShowImage()
OKDialog("Now into a stack...")
number sz = 10
img.ImageResize(3,sx,sy,sz) // All values are zero now!
img = iradius * Random()
I have 2 images that I need to plot in one figure then display the points of interest found with SURF on both images:
Image 1 : size [6113x5693x3]
Image 2 : size [4896x3744x3]
when trying to plot both of images in one figure with this code:
I = zeros([size(I1,1) size(I1,2)*2 size(I1,3)]);
I(:,1:size(I1,2),:)=I1;
I(:,size(I1,2)+1:size(I1,2)+size(I2,2),:)=I2;
figure, imshow(I); hold on;
and to display the points of interest of each one of them with :
plot([Pos1(:,2) Pos2(:,2)+size(I1,2)]',[Pos1(:,1) Pos2(:,1)]','-');
plot([Pos1(:,2) Pos2(:,2)+size(I1,2)]',[Pos1(:,1) Pos2(:,1)]','o');
I get this error and I dont know how to fixed :
Subscripted assignment dimension mismatch.
Any suggestion will be welcome!
Walk through this line by line. The error occurs on line 3. You are trying to assign I2 (with dimension 4896x3744x3) to a select part of I that has an incorrect first dimension (since the first dimension of I is the same as I1, not I2).
size(I(:,size(I1,2)+1:size(I1,2)+size(I2,2),:)) = [ 6113 3744 3 ]
size(I2) = [4896 3744 3]
I have a image.mat of about 4MB.
The size of some image file can also be 4MB.
Can the image.mat be transferred to image file?
I tried this, but that doesn't do the trick:
load image.mat %load Iw
imshow(mat2gray(Iw))
imwrite(Iw,'image.png');
IwNew = imread('image.png');
isequal(Iw,IwNew)
The result is 0; am I misunderstanding something?
The number in Iw are very important, so Iw can not be changed.
Actually my real problem is how to store float numbers into an image?
But MATLAB does not support Tiff 6.0, so I'll have to find some workaround.
I am doing a blind watermarking,and the decimal fraction of a number in Iw is important because it involve the information about another image.So the Iw can not be changed.
Actually,Mathematica can store floating floating-point data:
But my programs are all in MATLAB.
According to Matlab documentation:
"If A is a grayscale or RGB color image of data type double or single, then imwrite assumes that the dynamic range is [0,1] and automatically scales the data by 255 before writing it to the file as 8-bit values."
In other words: imwrite performs automatic conversion from double to uint8.
if you wish to keep the values of Iw unchanged, save it as a mat file and not as an image.
If you do want to save it as an image - there is going to be some loss of information. In this case, there are two things which need to be done:
Change the dynamic range of the matrix to [0,1]. (in your case, the range is between -0.0035 to 255.0035. Also, the matrix contain inf values).
If you want to get an equality, scale IwNew by 255, and convert it to uint8.
Code:
load image.mat %load Iw
%step 1, change the dynamic range of the image to [0,1].
%One way to do it is by using mat2gray on each channel separately.
Iw(:,:,1) = mat2gray(Iw(:,:,1));
Iw(:,:,2) = mat2gray(Iw(:,:,2));
Iw(:,:,3) = mat2gray(Iw(:,:,3));
%write the image to file
imwrite(Iw,'image.png');
%read the image
IwNew=imread('image.png');
%scale it, and convert to uint 8
Iw2 = uint8(Iw*255);
%check equality
isequal(Iw2,IwNew)
Result:
ans =
1
Alternatively, if you want to convert IwNew to double, perform the following:
%conversion to double
Iw2 = double(IwNew)/255;
Notice that in this case, the matrices won't be equal to one another,
Due to the loss of information which happened during the imwrite process (conversion from double to uint8).
Instead, they will be epsilon-close to one another, where epsilon = 0.0001.
In order to test this, write the following:
%equality check
sum(abs(Iw2(:)-Iw(:))>0.0001)
Result:
ans =
0
My MATLAB (R2010a) with the image processing toolbox is perfectly capable of storing double-valued pixel values, and retrieve them without loss of data.
Here's a shameless copy of this answer:
% Some random, data of type double
A = 7.6*rand(10);
% Construct TIFF image...
t = Tiff('test.tif', 'w');
% ...with these custom parameters...
tagstruct = struct(...
'ImageLength' , size(A,1),...
'ImageWidth' , size(A,2),...
'Compression' , Tiff.Compression.None,...
'SampleFormat' , Tiff.SampleFormat.IEEEFP,... % floating point
'Photometric' , Tiff.Photometric.MinIsBlack,...
'BitsPerSample' , 64,... % 8 bytes / double
'SamplesPerPixel' , 1,...
'PlanarConfiguration', Tiff.PlanarConfiguration.Chunky);
t.setTag(tagstruct);
% ...and write it to disk.
t.write(A);
t.close();
% Read the data actually written, and check if all
% information was indeed preserved:
B = imread('test.tif');
isequal(A,B)
Result:
ans =
1
Adjust in obvious ways if you have more than 1 channel (RGB).
I am working on a project where i have to first normalize the image i.e convert the pixel range of my image from 16-235 (as it is only luminance component of the image , pixel values are always defined in the range 16-235) to 0 - 1 then i perform dwt and idwt on the image after the processing i want to again maps these pixels values from 0 - 1 to 16 - 235. ie if the pixel value is 1 value then it should be stored in the image matrix as 235.
for which i tried the following matlab code ,this code works perfectly fine when i denormalize the image immediately after normalization , but output becomes complete white if i use this code after performing dwt and idwt.
for j = 1:1:361
for k=1:1:361 %dimensions of my matrix
if(distorted1(j,k)~=0)
temp=distorted1(j,k);
temp1=temp/0.0045;
distorted1(j,k)=int8(temp1)+1;
end
end
end
imshow(distorted1);
it seems like the result of your idwt is of type double ( or single ) and not int anymore. convert to uint8 and then imshow it.
Trying to imshow an image of type double/single will saturate all pixels with values larger than 1.0 (rather than 255 for images of type int).
I'm working with some MRI data in Matlab 2014b, but the data is formed of intensity values not RGB. To get around this I use the code below to form a movie out of the MRI frames (I'm working on dynamic data here)
My problem is that the images need to have altered display values for the pixels, as the default only displays between -Inf and Inf, and I need between 0 and 0.25 to get a sensible image out of my data.
Are there any ways to pass that change from the script in to the movie, and then to write to file? I can only seem to do this per image in implay, and I'd like an automated way to edit each image and then store as a frame for a movie..?
%Code for producing movie.
graymap = gray(256);
for i = 1:32
a(:,:,i) = cmunique(Reformed_Data_Colourmap(:,:,i));
end
for i = 1:32
b = im2frame(a(:,:,i),graymap);
a(:,:,1) = ((b.cdata));
image(a(:,:,1))
colormap 'gray'
%The change needs to be here, to display pixel values from 0 to 0.25, to allow for a sensible image from the MR data.
frames(1,i) = getframe;
end
movie(frames)
The solution is provided:
for i = 1:32
b = im2frame(a(:,:,i),graymap);
a(:,:,1) = ((b.cdata));
clims = [0 250];
%image(a(:,:,1),clims)
colormap 'gray'
imagesc(a(:,:,1),clims);
%set('window', [0 400])
frames(1,i) = getframe;
end
clims solves the issue.