Determining the length of an image and a portion of it

Question

I am trying to get the length of an image as well as the length of a portion of it, but both give the same result. Where did I go wrong?

Part of area of image:

private BufferedImage add_text(BufferedImage image, String text) {
    BufferedImage imageLocation=image.getSubimage(image.getWidth()/2, image.getHeight()/2, 
            image.getWidth()-image.getWidth()/2, image.getHeight()-image.getHeight()/2);

    byte img[] = get_byte_data(imageLocation);
    System.out.println("Image length: "+img.length);

Whole image:

private BufferedImage add_text(BufferedImage image, String text) {

    byte img[] = get_byte_data(image);
    System.out.println("Image length: "+img.length);

The output of both is

Image length: 984900

Here you are getting length of the byte array. Not the actual image.You should use imageLocation.getWidth() and imageLocation.getHeight(). — Don Srinath, Jan 15 '14 at 04:27
if you want to get size of a portion of image in bytes in a particular format (lets say JPEG) u need to create a new bitmap copy the contents you want( the portion of the image ) and then store that as byte stream in a MemeoryStream object and then get length. If this is indeed your question — Pulkit Sethi, Jan 15 '14 at 04:35
Sorry, my poor English. It should be getting length of the image byte array. — Jarek Huang, Jan 15 '14 at 04:54

score 0 · Accepted Answer · answered Jan 15 '14 at 04:35

0

Here you are getting length of the byte array. Not the actual image. You should use imageLocation.getWidth() and imageLocation.getHeight().

If you have checked the java doc http://docs.oracle.com/javase/7/docs/api/java/awt/image/BufferedImage.html it says that getSubimage method shares the same data array as the original image. That is why you are getting same length for the data array length.

answered Jan 15 '14 at 04:35

Don Srinath

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Thank you Srinath. But i have a question, because i want to put a message in this part of area, so i need to exactly location of this area. `private byte[] get_byte_data(BufferedImage image) { WritableRaster raster = image.getRaster();` In this image here is the original image?? or the part of image?? – Jarek Huang Jan 15 '14 at 05:07
@JarekHuang , if you just need to print some text on the original image it's much more easier. Check the answer for this question. http://stackoverflow.com/questions/2658554/using-graphics2d-to-overlay-text-on-a-bufferedimage-and-return-a-bufferedimage – Don Srinath Jan 15 '14 at 05:23
Actually, i am trying to put the invisible message into the image, but i want to put it to difference part of image. This is a link i am asking [link]http://stackoverflow.com/questions/21127860/put-invisible-message-in-four-part-of-image-by-using-raster – Jarek Huang Jan 15 '14 at 05:54
Because i need to know the x - the X coordinate of the upper-left corner of the specified rectangular region y - the Y coordinate of the upper-left corner of the specified rectangular region w - the width of the specified rectangular region h - the height of the specified rectangular region if i just use `imageLocation.getWidth() and imageLocation.getHeight()` , it will not have exactly rectangular region i wanted. – Jarek Huang Jan 15 '14 at 05:56
@JarekHuang I think you have mixed up Steganography concepts and Java image manipulation. I'll answer your other question on Steganography since it doesn't relate directly to this question. – Don Srinath Jan 25 '14 at 05:26

Determining the length of an image and a portion of it

1 Answers1