Java: Rotating Images

Question

I need to be able to rotate images individually(in java). The only thing I have found so far is g2d.drawImage(image, affinetransform, ImageObserver ). Unfortunately, I need to draw the image at a specific point, and there is no method with an argument that 1.rotates the image separately and 2. allows me to set the x and y. any help is appreciated

Shortening

Please see: Why is “Can someone help me?” not an actual question? – Willson

Answer 1

This is how you can do it. This code assumes the existance of a buffered image called 'image' (like your comment says)

// The required drawing location
int drawLocationX = 300;
int drawLocationY = 300;

// Rotation information

double rotationRequired = Math.toRadians (45);
double locationX = image.getWidth() / 2;
double locationY = image.getHeight() / 2;
AffineTransform tx = AffineTransform.getRotateInstance(rotationRequired, locationX, locationY);
AffineTransformOp op = new AffineTransformOp(tx, AffineTransformOp.TYPE_BILINEAR);

// Drawing the rotated image at the required drawing locations
g2d.drawImage(op.filter(image, null), drawLocationX, drawLocationY, null);

Pilcomayo

Why so complex? The transform contains both rotation and translation, so just do g2d.drawImage(image, tx, ImageObserver) with the tx from answer. – Regatta

Thanks, but it cuts off some of the image. – Como

Any info on how to circumvent the cutoff problem? – Capitular

Answer 2

AffineTransform instances can be concatenated (added together). Therefore you can have a transform that combines 'shift to origin', 'rotate' and 'shift back to desired position'.

Esparto

Answer 3

I struggled a little with the existing answers because my image to be rotated is not always a square, furthermore the accepted answer has a comment asking "Any info on how to circumvent the cutoff problem" that is not answered. So for those who had the issue of image being croped when rotated here is the code that worked for me :

public static BufferedImage rotate(BufferedImage bimg, Double angle) {
    double sin = Math.abs(Math.sin(Math.toRadians(angle))),
           cos = Math.abs(Math.cos(Math.toRadians(angle)));
    int w = bimg.getWidth();
    int h = bimg.getHeight();
    int neww = (int) Math.floor(w*cos + h*sin),
        newh = (int) Math.floor(h*cos + w*sin);
    BufferedImage rotated = new BufferedImage(neww, newh, bimg.getType());
    Graphics2D graphic = rotated.createGraphics();
    graphic.translate((neww-w)/2, (newh-h)/2);
    graphic.rotate(Math.toRadians(angle), w/2, h/2);
    graphic.drawRenderedImage(bimg, null);
    graphic.dispose();
    return rotated;
}

Primine

Hey, it worked for me. The only issue is that I can't get it to rotate around a certain point. How should I do this? – Fieldfare

Answer 4

A simple way to do it without the use of such a complicated draw statement:

    //Make a backup so that we can reset our graphics object after using it.
    AffineTransform backup = g2d.getTransform();
    //rx is the x coordinate for rotation, ry is the y coordinate for rotation, and angle
    //is the angle to rotate the image. If you want to rotate around the center of an image,
    //use the image's center x and y coordinates for rx and ry.
    AffineTransform a = AffineTransform.getRotateInstance(angle, rx, ry);
    //Set our Graphics2D object to the transform
    g2d.setTransform(a);
    //Draw our image like normal
    g2d.drawImage(image, x, y, null);
    //Reset our graphics object so we can draw with it again.
    g2d.setTransform(backup);

Benally

Answer 5

public static BufferedImage rotateCw( BufferedImage img )
{
    int         width  = img.getWidth();
    int         height = img.getHeight();
    BufferedImage   newImage = new BufferedImage( height, width, img.getType() );

    for( int i=0 ; i < width ; i++ )
        for( int j=0 ; j < height ; j++ )
            newImage.setRGB( height-1-j, i, img.getRGB(i,j) );

    return newImage;
}

from https://coderanch.com/t/485958/java/Rotating-buffered-image

Amatol

Answer 6

Here is a solution for rotations of 90, 180 & 270 degrees.

For these cases, the AffineTransform can introduce some loss/interpolation.

This solution is lossless & can also handle (esoteric?) Colour Models with more than 8 Bits/Pixel which BufferedImage.getRGB(int x, int y) cannot.

The solution proceeds on a pixel-by-pixel basis, which has the advantage of being simple to code.

It is possible to read the original Image row-by-row to gain performance, but its more complex, so I've left that out.

import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
/**
 * N.B. this example uses the new switch/case/Arrow notation, which requires Java 14.
 */
public enum Rotation {
    CLOCKWISE_90,
    CLOCKWISE_180,
    CLOCKWISE_270;

    public BufferedImage rotate(final BufferedImage original) {

        final int oW = original.getWidth();
        final int oH = original.getHeight();

        final BufferedImage rotated = 
        switch (this) {
            case CLOCKWISE_180 -> new BufferedImage(oW, oH, original.getType());
            default            -> new BufferedImage(oH, oW, original.getType());
        };

        final WritableRaster rasterOriginal = original.copyData(null);
        final WritableRaster rasterRotated  = rotated .copyData(null);
        /*
         * The Data for 1 Pixel...
         */
        final int[] onePixel = new int[original.getSampleModel().getNumBands()];
        /*
         * Copy the Pixels one-by-one into the result...
         */
        for     (int x = 0; x < oW; x++)  {
            for (int y = 0; y < oH; y++)  {
                ;                         rasterOriginal.getPixel(         x,          y, onePixel);
                switch (this) {
                    case CLOCKWISE_90  -> rasterRotated .setPixel(oH - 1 - y,          x, onePixel);
                    case CLOCKWISE_270 -> rasterRotated .setPixel(         y, oW - 1 - x, onePixel);
                    default            -> rasterRotated .setPixel(oW - 1 - x, oH - 1 - y, onePixel);
                };
            }
        }
        rotated.setData(rasterRotated);

        return rotated;
    }
}

Turnbuckle

Answer 7

Sorry, but all the answers are difficult to understand for me as a beginner in graphics...

After some fiddling, this is working for me and it is easy to reason about.

@Override
public void draw(Graphics2D g) {
    AffineTransform tr = new AffineTransform();
    // X and Y are the coordinates of the image
    tr.translate((int)getX(), (int)getY());
    tr.rotate(
            Math.toRadians(this.rotationAngle),
            img.getWidth() / 2,
            img.getHeight() / 2
    );

    // img is a BufferedImage instance
    g.drawImage(img, tr, null);
}

I suppose that if you want to rotate a rectangular image this method wont work and will cut the image, but I thing you should create square png images and rotate that.

Epiphytotic

Answer 8

I think the sturdiest and easiest approach is to not only rotate the image, but also the coordinates you're working with. This code will turn a bufferedImage around the topleft corner and draw it accordingly without cropping, and the returned image will be drawn in the right place. If you know what a vector and matrix are and look at the wikipedia article for rotation matrix you will understand this code easily. I also added a little hand drawing to it. In the 2nd part of the algorithm we determine the position and dimension of the bigger rectangle, which contains our rotated bufferedImage. The first 4 points we define are technically not used, but they still help you understand where the points are initially.

public void drawRotated(final Graphics g, final BufferedImage bufferedImage, final int x, final int y, final int width, final int height, final double angle) {
    final Rectangle collision = new Rectangle(x, y, width, height);
    final BufferedImage resize = resize(bufferedImage, collision.width, collision.height);
    final BufferedImage rotate = rotate(resize, angle, collision);
    g.drawImage(rotate, collision.x, collision.y, collision.width, collision.height, null);
}

public static BufferedImage resize(final BufferedImage bufferedImage, final int newWidth, final int newHeight) {
    final BufferedImage resized = new BufferedImage(newWidth, newHeight, bufferedImage.getType());
    final Graphics g = resized.createGraphics();
    g.drawImage(bufferedImage, 0, 0, newWidth, newHeight, null);
    return resized;
}

public static BufferedImage rotate(final BufferedImage bufferedImage, final double angle, final Rectangle collision) {
    final double sin = Math.sin(Math.toRadians(angle));
    final double cos = Math.cos(Math.toRadians(angle));
    
    final int x1 = collision.x;
    final int y1 = collision.y;
    
    final int x2 = collision.x+collision.width;
    final int y2 = collision.y;
    
    final int x3 = collision.x;
    final int y3 = collision.y+collision.height;
    
    final int x4 = collision.x+collision.width;
    final int y4 = collision.y+collision.height;
    
    //turn all 4 points around the top left point
    final int newx1 = collision.x;
    final int newy1 = collision.y;
    
    //the y component is 0
    final int newx2 = (int) (collision.x+collision.width*cos);
    final int newy2 = (int) (collision.y+collision.width*sin);
    
    //the x component is 0
    final int newx3 = (int) (collision.x-collision.height*sin);
    final int newy3 = (int) (collision.y+collision.height*cos);

    final int newx4 = (int) (collision.x+collision.width*cos-collision.height*sin);
    final int newy4 = (int) (collision.y+collision.width*sin+collision.height*cos);
    
    //determine the new position of our bigger rectangle containing our image
    collision.x = Math.min(Math.min(newx1, newx2), Math.min(newx3, newx4));
    collision.y = Math.min(Math.min(newy1, newy2), Math.min(newy3, newy4));
    
    //determine the new dimensions of our bigger rectangle containing our image
    collision.width = Math.max(Math.max(newx1, newx2), Math.max(newx3, newx4))-collision.x;
    collision.height = Math.max(Math.max(newy1, newy2), Math.max(newy3, newy4))-collision.y;
    
    final BufferedImage rotated = new BufferedImage(collision.width, collision.height, bufferedImage.getType());
    final Graphics2D g2d = rotated.createGraphics();
    g2d.translate(newx1- collision.x, newy1- collision.y);
    g2d.rotate(Math.toRadians(angle), 0, 0);
    g2d.drawRenderedImage(bufferedImage, null);
    g2d.dispose();
    return rotated;
}

Coretta