I am trying to properly convert a RAW image so that I can view it in MATLAB. Image can be downloaded here. I am using the version of the code provided in How can I read in a RAW image in MATLAB?
However, it is not working properly for me. Here is my slightly modified version below:
clear;
row=966; col=1296;
fin=fopen('C:\Users\user\Desktop\test2.raw','r');
I=fread(fin, col*row*3,'uint8=>uint8'); %// Read in as a single byte stream
I = reshape(I, [col row 3]); %// Reshape so that it's a 3D matrix - Note that this is column major
Ifinal = flipdim(imrotate(I, -90),2); % // The clever transpose
imshow(Ifinal);
fclose(fin); %// Close the file
What I get:
What I should get:
I'm not sure why it's not working for me but if I use an imaging program (ImageJ) I can correctly convert the RAW file if I select Image type as '24-bit BGR'. The pixel format of the image is 8 Bit BAYRG.
There you go:
function q43127920
row=966; col=1296;
fin=fopen('test.raw','r');
I = fread(fin, col*row*3,'ubit24=>uint32');
I = reshape(I, col, row, []);
B = uint8(bitand(bitshift(I,-00),uint32(255)));
G = uint8(bitand(bitshift(I,-08),uint32(255)));
R = uint8(bitand(bitshift(I,-16),uint32(255)));
I = cat(3,R,G,B);
Ifinal = flip(imrotate(I, -90),2);
imagesc(Ifinal);
fclose(fin);
Result:
Related
I'm using the following code to show an image from array which previously converted to array. But the image not show correctly:
I = imread('ut.jpg');
image=mat2gray(I);
imshow(image);
FID = fopen('FileName.txt', 'w');
if FID == -1, error('Cannot create file.'); end
fprintf(FID, '%g %g %g ... %g \n', image);
fclose(FID);
x = 100*rand(512,1500);
fileID = fopen('FileName.txt','w');
fprintf(fileID,'%f',x);
fclose(fileID);
imshow(x);
Bitmaps consist of two things. First: 3 matrices with colour intensities, graduated as uint, numbers from 0 to 255. Second: A header containing information regarding size, colordepth, filelength, etc.
Your program does not create correct images because it misses a header.
Regarding the matlab procedure:
By using imread on a RGB image, you are automatically creating a matrix. If you convert it to grayscale with rgb2gray you will have a single matrix of uint (without any additional layers).
If you want to safe your image after processing it simply use:
I = imread('ut.jpg');
% Convert, do smth e.g. I_new = rgb2gray(I);
filename = 'myNewImage.jpg';
imwrite(I_new,filename);
By using imwrite you automatically create a correct header.
I'm trying to extract a (very) large number of subimages from a large grayscale TIF file and save each image as a GIF, PNG, or even another TIF using MATLAB. I'm able to display the individual images using imshow(sub(:,:,1),cmap) but when I try to write the data to an image file, the generated files are just white squares 101x101 px. Using the cmap argument in imwrite produces the same result, as does changing the image format (I've tried with PNG, TIF, GIF, and JPG with no luck). The file a.tif is 16 bit according to the property menu in Windows Explorer. Any help is appreciated. I'm really at wit's end with this.
% Import coordinates array and correct for multiplication by 10
datafile = 'data.xlsx';
coords = xlsread(datafile,1,'G2:H13057');
x = coords(:,1) ./ 10;
y = coords(:,2) ./ 10;
r = 50;
[img, cmap] = imread('a.tif'); % import the image
s = 2*r+1; % scalar of size of each submatrix in the array (sise of image)
sub = zeros(s,s,num); % create 3D matrix/array of matrices. Each submatrix corresponds to 50 px box around each point
i = 1:4;
subrgb = zeros(s,s,num);
for i=1:4
sub(:,:,i) = img((y(i)-r):(y(i)+r),(x(i)-r):(x(i)+r));
filename = 'dot_%d.png';
filename = sprintf(filename,i);
imwrite(sub(:,:,i),filename,'png');
end
Try changing the line:
sub = zeros(s,s,num);
to:
sub = zeros(s,s,num,class(img));
I assume that the problem is that sub is of type double.
Good luck
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'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.
I have a real time application which receives jpg images coded in base64. I do not know how to show the image in matlab without having to save the image in the disk and open it afterwards.
This is the code I have so far, that saves the image in the disk before showing it:
raw = base64decode(imageBase64, '', 'java');
fid = fopen('buffer.jpg', 'wb');
fwrite(fid, raw, 'uint8');
fclose(fid);
I = imread('buffer.jpg');
imshow(I);
Thanks!
You can do it with the help of Java. Example:
% get a stream of bytes representing an endcoded JPEG image
% (in your case you have this by decoding the base64 string)
fid = fopen('test.jpg', 'rb');
b = fread(fid, Inf, '*uint8');
fclose(fid);
% decode image stream using Java
jImg = javax.imageio.ImageIO.read(java.io.ByteArrayInputStream(b));
h = jImg.getHeight;
w = jImg.getWidth;
% convert Java Image to MATLAB image
p = reshape(typecast(jImg.getData.getDataStorage, 'uint8'), [3,w,h]);
img = cat(3, ...
transpose(reshape(p(3,:,:), [w,h])), ...
transpose(reshape(p(2,:,:), [w,h])), ...
transpose(reshape(p(1,:,:), [w,h])));
% check results against directly reading the image using IMREAD
img2 = imread('test.jpg');
assert(isequal(img,img2))
The first part of decoding the JPEG byte stream is based on this answer:
JPEG decoding when data is given in array
The last part converting Java images to MATLAB was based on this solution page:
How can I convert a "Java Image" object into a MATLAB image matrix?
That last part could also be re-written as:
p = typecast(jImg.getData.getDataStorage, 'uint8');
img = permute(reshape(p, [3 w h]), [3 2 1]);
img = img(:,:,[3 2 1]);
imshow(img)