How can a change image format like .jpg to .png by using loops and with out use of 'imwrite' command

In MATLAB we have a command "IMWRITE" to change the format but my problem is what's going behind, when we are using 'IMWRITE' command in the program.

Answer 1

[Stephen23]

imwrite does not require any toolboxes (it is standard MATLAB), so why do you not want to use it?

If you want an alternative, consider Oliver Woodford and Yair Altman's highly regarded FEX submission:

https://www.mathworks.com/matlabcentral/fileexchange/23629-export-fig

[venkata ravi vusa]

Thank you sir Actually i have to make my program without 'IMWRITE' command. it's part of a project

[Image Analyst]

Then you'll have to look up the official format and use fwrite() to write out the image "manually" byte by byte yourself, that is, if you're allowed to use fopen(), fwrite(), and fclose().

[Walter Roberson]

Please post the specific requirements of the project. There is no point in our making proposals that might be rejected because you forgot to mention a restriction.

For example if the reason you cannot use imwrite is that you need generate code for an FPGA and that does not support imwrite then that would be important information because FPGA does not support file i/o at all.

Answer 2

[KSSV]

You can rename your image file .jpg to .png. doc movefile.

[Stephen23]

@KSSV: that will rename the file, but it will not convert the image format as the question requests.

[KSSV]

When I want to change the type of file, I will rename the extension with matlab opened. If we rename with extension won't it change?

[Stephen23]

"If we rename with extension won't it change?"

Dr. Siva Srinivas Kolukula: how would it do this? Why would changing the string of the filename (which is solely a feature of the OS) make any change to the encoding of the file (which is a collection of bits arranged according to a particular standard)? Did you even try this?

Your doctorate should have taught you that you can investigate things like this yourself: it would only take one minute. Create a text document with .txt extension. Now rename the file to .ppt: did it magically become a powerpoint presentation? Did the entire file get re-encoded? How? By what codecs?

If you actually read the movefile documentation, does it mention any words such as "format", "change", "re-encode", "codec", or anything similar? Or does it instead explain clearly that it moves and renames files?

"When I want to change the type of file, I will rename the extension with matlab opened."

Show me one example of when that has changed the format (i.e. file encoding) of a file (I hope you are not going to tell me that .csv and .txt are different file formats).

[KSSV]

It is a common sense that .txt cannot be changed to .ppt merely changing the extension. I was talking about images. Can't .jpg image image changes to .bmp or .png by changing the extension?

And yes my doctorate didn't teach me anything.

[Stephen23]

"Can't .jpg image image changes to .bmp or .png by changing the extension?"

Changing the file extension just changes the file extension. It does not change the file encoding. Try it.

[KSSV]

Okay.....Will get back to you on Monday.

[Stephen23]

>> X = ones(1,1,3)/2;
>> imwrite(X,'test.jpg','jpg');
>> S = imfinfo('test.jpg'); S.Format
ans =
jpg
>> movefile('test.jpg','test.png')
>> S = imfinfo('test.png'); S.Format
ans =
jpg

Changed the file extension, no change in file format.

To Anyone Else: this "answer" does not work

[KSSV]

@ Stephen Cobeldick

I have checked renaming file within matlab and without matlab and then used iminfo, yes the format didn't change.

Your doctorate should have taught you that you can investigate things like this yourself: it would only take one minute. I was renaming image files like this earlier for web uploads, I was in misconception. Thank you for for the point.