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Thread: Image to file and contra

  1. #1
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    Default Image to file and contra

    Is there any way to write an array of images into file ( for example text file) and read them from file (in Java of course).


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Image to file and contra

    Yes. You can write images to a file, by concatenating one after the other. I think you'd need a record length field to keep track of each separate image.
    Why do you want them in a text file? Images are composed of binary data that is useless to view in a text editor.
    If you need to convert the bytes of the images to text, look at Base64 encoding.

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    Default Re: Image to file and contra

    I am making project and its GUI needs to show some images (that can be changed in program) and then I want to save them back. Saving images in folder "Images" and something like that will make things more difficult (difficulties with picture names etc...) I use the following program:

    [highlight]
    BufferedImage image=ImageIO.read(new File(legal file path));
     
    ByteArrayOutputStream baos=new ByteArrayOutputStream();
            ImageIO.write(image, "jpg", baos);
            byte[] bitii=baos.toByteArray();
            FileOutputStream f=new FileOutputStream(new File(legal file path));
            f.write(biti);
     
    [/highlight]

    Yesterday it did not work properly, today it works norm can I use a hint of placing 1 or more empty lines between two different images and then read first one until I reach empty line and so on?

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    Default Re: Image to file and contra

    I would recommend against writing multiple images to the same file. Instead, create multiple files with one image per file.

    To read/write images, see this post: Images (read/write and drawing)

  5. #5
    Super Moderator Norm's Avatar
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    Default Re: Image to file and contra

    What byte makes an empty line? The new line character? Since the image is binary, it can contain any byte value including the newline character. It could be most images would not have 3 newline characters in a row. But it is not impossible.

    For an exercise: Write an image to a byte array. Create a histogram of the bytes used in an image by writing a loop to go thru that byte array and use the value of the byte to increment/count occurances. Then print out the results. For example:
    byte[] theImage // the array with the image bytes
    int[] histogram = new int[256]; // the byte usage counters
     
    for(int i =0; i < theImage.length; i++) {
      histogram[theImage[i] & 0xFF]++; // count usage of this byte from the image
    }
    System.out.println("histo=" + Arrays.toString(histogram));  // show the counts
    Last edited by Norm; August 29th, 2010 at 03:20 PM. Reason: Use int and add & 0xFF

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    Default Re: Image to file and contra

    Or use a ZipOutputStream and write the images as separate ZipEntries to a ZipFile.

    db

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    Default Re: Image to file and contra

    Thanks for advices.

    I have also found Base64 encoder and decoder at Encode/Decode to/from Base64 - Real's Java How-to and downloaded java mail from https://cds.sun.com/is-bin/INTERSHOP...-CDS_Developer
    and how can I add this classes ( something like library) to be used in my project .
    I tried to add this one to bootstrap entries (I am using Eclipse) but import of javax.mail.internet.MimeUtility is not recognized yet ?

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    Super Moderator Norm's Avatar
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    Default Re: Image to file and contra

    Why do you want the image's bytes to be output to a text file? Is this a student exercise to see how to do something?

    Sorry, I have no idea how to configure your IDE.

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    Default Re: Image to file and contra

    I am doing Java project in which each user should have its own picture that can be changed and I have to save these changes Since there can be many many users it can become a little bit difficult to deal with all these pictures and I wanted to write them in just one tex file but I have forsaken this idea (because it is a little bit complicated and I do not have too much time now to deal with all these conversions + javax.mail.internet.MimeUtility not recognized and so on) and will save each image separately in one folder.

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    Default Re: Image to file and contra

    You still haven't explained why you want to use a TEXT file. If that requirement is not part of some learning assignment, it's a downright stupid approach.

    db

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    Default Re: Image to file and contra

    Darryl.Burke I think that you have not read my first post carefully I wrote : for example text file It can be any type of file but aim is to have just one file instead of many pictures. I am also sure that it will increase my project points and of course I want to learn how to do this (not just for project points).

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    Super Moderator Norm's Avatar
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    Default Re: Image to file and contra

    user should have its own picture that can be changed and I have to save these changes
    How will the images be changed if they are all in one file? To change any one image in the file, you will have to write out the file with all of the images.

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    Default Re: Image to file and contra

    norm When program starts, it reads all of images from file Then a frame containing combo box for name selection is drawn. And if for example John Norm is selected then panel containing his picture and some infos is shown. We can change a picture that is shown and when we close application all these pictures should be saved back into file from which they were read.

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    Super Moderator Norm's Avatar
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    Default Re: Image to file and contra

    Ok that could work if you read ALL of the images in at the start and write all of the images out at the end and don't do any I/O to the images file while the program is running.

    I'm attaching a zip with a project I did a while back that does something like you are trying to do. I had a web site that restricted the number of files I could post. It did allow jar files and .dat files. So I put all the images in one file vs have separate files for each image. Enjoy.

    Norm
    Attached Files Attached Files
    Last edited by Norm; August 31st, 2010 at 10:44 AM.

  15. The Following User Says Thank You to Norm For This Useful Post:

    Javabeginner (September 2nd, 2010)

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    Default Re: Image to file and contra

    Thanks for post.

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