How do I crop an image in Java

Question

I want to crop an image manually using the mouse  Suppose the image has some text  and I want to select some text from an image  then  for that purpose I want to crop that area by using the mouse

User · Answer

I m giving this example because this actually work for my use case   I was trying to use the AWS Rekognition API  The API returns a BoundingBox object   BoundingBox boundingBox   faceDetail getBoundingBox      The code below uses it to crop the image   import com amazonaws services rekognition model BoundingBox   private BufferedImage cropImage BufferedImage image  BoundingBox box            Rectangle goal   new Rectangle Math round box getLeft    image getWidth    Math round box getTop    image getHeight    Math round box getWidth     image getWidth     Math round box getHeight     image getHeight               Rectangle clip   goal intersection new Rectangle image getWidth    image getHeight               BufferedImage clippedImg   image getSubimage clip x  clip y   clip width  clip height            return clippedImg

User · Answer

You need to read about Java Image API and mouse-related API  maybe somewhere under the java awt event package    For a start  you need to be able to load and display the image to the screen  maybe you ll use a JPanel    Then from there  you will try implement a mouse motion listener interface and other related interfaces  Maybe you ll get tied on the mouseDragged method     For a mousedragged action  you will get the coordinate of the rectangle form by the drag     Then from these coordinates  you will get the subimage from the image you have and you sort of redraw it anew      And then display the cropped image    I don t know if this will work  just a product of my imagination    just a thought

User · Answer

This is a method which will work   import java awt image BufferedImage  import java awt Rectangle  import java awt Color  import java awt Graphics   public BufferedImage crop BufferedImage src  Rectangle rect        BufferedImage dest   new BufferedImage rect getWidth    rect getHeight    BufferedImage TYPE ARGB PRE       Graphics g   dest getGraphics        g drawImage src  0  0  rect getWidth    rect getHeight    rect getX    rect getY    rect getX     rect getWidth    rect getY     rect getHeight    null       g dispose        return dest      Of course you have to make your own JComponent   import java awt event MouseListener  import java awt event MouseMotionListener  import java awt image BufferedImage  import java awt Rectangle  import java awt Graphics  import javax swing JComponent   public class JImageCropComponent extends JComponent implements MouseListener  MouseMotionListener      private BufferedImage img     private int x1  y1  x2  y2      public JImageCropComponent BufferedImage img              this img   img         this addMouseListener this          this addMouseMotionListener this            public void setImage BufferedImage img              this img   img           public BufferedImage getImage               return this            Override    public void paintComponent Graphics g             g drawImage img  0  0  this         if  cropping                       Paint the area we are going to crop            g setColor Color RED             g drawRect Math min x1  x2   Math min y1  y2   Math max x1  x2   Math max y1  y2                      Override    public void mousePressed MouseEvent evt              this x1   evt getX           this y1   evt getY              Override    public void mouseReleased MouseEvent evt              this cropping   false            Now we crop the image            This is the method a wrote in the other snipped        BufferedImage cropped   crop new Rectangle Math min x1  x2   Math min y1  y2   Math max x1  x2   Math max y1  y2              Now you have the cropped image            You have to choose what you want to do with it        this img   cropped            Override    public void mouseDragged MouseEvent evt              cropping   true         this x2   evt getX           this y2   evt getY               TODO  Implement the other unused methods from Mouse Motion Listener      I didn t test it  Maybe there are some mistakes  I m not sure about all the imports    You can put the crop img  rect  method in this class  Hope this helps

User · Answer

There are two potentially major problem with the leading answer to this question  First  as per the docs       public BufferedImage getSubimage int x                            int y                            int w                            int h       Returns a subimage defined by a specified rectangular region     The returned BufferedImage shares the same data array as the original   image    Essentially  what this means is that result from getSubimage acts as a pointer which points at a subsection of the original image   Why is this important  Well  if you are planning to edit the subimage for any reason  the edits will also happen to the original image  For example  I ran into this problem when I was using the smaller image in a separate window to zoom in on the original image   kind of like a magnifying glass   I made it possible to invert the colors to see certain details more easily  but the area that was  zoomed  also got inverted in the original image  So there was a small section of the original image that had inverted colors while the rest of it remained normal  In many cases  this won t matter  but if you want to edit the image  or if you just want a copy of the cropped section  you might want to consider a method   Which brings us to the second problem  Fortunately  it is not as big a problem as the first  getSubImage shares the same data array as the original image  That means that the entire original image is still stored in memory  Assuming that by  crop  the image you actually want a smaller image  you will need to redraw it as a new image rather than just get the subimage   Try this   BufferedImage img   image getSubimage startX  startY  endX  endY     fill in the corners of the desired crop location here BufferedImage copyOfImage   new BufferedImage img getWidth    img getHeight    BufferedImage TYPE INT RGB   Graphics g   copyOfImage createGraphics    g drawImage img  0  0  null   return copyOfImage    or use it however you want   This technique will give you the cropped image you are looking for by itself  without the link back to the original image  This will preserve the integrity of the original image as well as save you the memory overhead of storing the larger image   If you do dump the original image later

User · Answer

File fileToWrite   new File filePath   url     BufferedImage bufferedImage   cropImage fileToWrite  x  y  w  h    private BufferedImage cropImage File filePath  int x  int y  int w  int h        try           BufferedImage originalImgage   ImageIO read filePath            BufferedImage subImgage   originalImgage getSubimage x  y  w  h              return subImgage        catch  IOException e            e printStackTrace            return null

User · Answer

The solution I found most useful for cropping a buffered image uses the getSubImage x y w h    My cropping routine ended up looking like this      private BufferedImage cropImage BufferedImage src  Rectangle rect          BufferedImage dest   src getSubimage 0  0  rect width  rect height         return dest

User · Answer

This question has not enough information to answer  A general solution  depending on your GUI framework   add a mouse event handler that will catch clicks and mouse movements  This will give you your  x  y  coordinates  Next use these coordinates to crop your image

[java] How do I crop an image in Java?

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