Using imwrite after DWT and IDWT

I am having a problem while using imwrite after performing DWT and IDWT operations on an gray image.

the problem is that after the imwrite operation when i click on the resulting image file all that i am able to view is a white background instead of an image.

Is there any method to overcome this problem.

for example: if x is an m*n gray scale image then what i have done is

[A,B,C,D]=dwt2(x,'haar');

.....

.....

.....

here i have done some manipulations on the sub-bands(B,C,D)

.....

.....

.....

y=idwt2(A,B,C,D,'haar');

imwrite(y,'C:\Users\HOME\Desktop\IMAGEPROCESS','jpg');

After all these operations when i use imshow(y,[]) the correct image is being displayed. But its not the same case when i try to open the JPG image file(named IMAGEPROCESS in the Eg) as a result of the imwrite operation.

KINDLY HELP

Answer 1

[Wayne King]

Hi Vikas, Interesting application.

Your problem is just scaling before you write the .jpg file. Without scaling, virtually all the elements of your image matrix are written to the value 255 in the .jpg file, which is why it appears all white when you display.

Execute these lines:

x = idwt2(CA,CH,CV,CD,'haar');
x = x/255;
imwrite(x,'C:\Users\HOME\Desktop\imageprocess.jpg','jpg');
Im = imread('C:\Users\HOME\Desktop\imageprocess.jpg');
imshow(Im,[]);

Hope that helps

[vikas]

Hey Wayne Thank You very much

Answer 2

[Wayne King]

imwrite() converts images to RGB before writing a jpeg file.

Can you please try writing a .png file and see if you have the same problem?

[vikas]

Dear Wayne,

I am still facing the same problem

[Wayne King]

Are you viewing the image written by imwrite in MATLAB, or using other software?

[vikas]

Yes i am using MATLAB

[Wayne King]

Hi Vikas, can you go over to CSSM and there you will see my email. Send me the original image along with the MATLAB code you use to manipulate the coefficients and I will have a look. It's hard to go further without more information.