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package java.awt.image;

import java.awt.image.ImageConsumer;
import java.awt.image.ColorModel;
import java.util.Hashtable;
import java.awt.Rectangle;


An ImageFilter class for cropping images.
This class extends the basic ImageFilter Class to extract a given
rectangular region of an existing Image and provide a source for a
new image containing just the extracted region.  It is meant to
be used in conjunction with a FilteredImageSource object to produce
cropped versions of existing images.

Author:     Jim Graham
See Also:
/**
 * An ImageFilter class for cropping images.
 * This class extends the basic ImageFilter Class to extract a given
 * rectangular region of an existing Image and provide a source for a
 * new image containing just the extracted region.  It is meant to
 * be used in conjunction with a FilteredImageSource object to produce
 * cropped versions of existing images.
 *
 * @see FilteredImageSource
 * @see ImageFilter
 *
 * @author      Jim Graham
 */
public class CropImageFilter extends ImageFilter {
    int cropX;
    int cropY;
    int cropW;
    int cropH;

    
Constructs a CropImageFilter that extracts the absolute rectangular
region of pixels from its source Image as specified by the x, y,
w, and h parameters.

Params:
  • x – the x location of the top of the rectangle to be extracted
  • y – the y location of the top of the rectangle to be extracted
  • w – the width of the rectangle to be extracted
  • h – the height of the rectangle to be extracted
/**
     * Constructs a CropImageFilter that extracts the absolute rectangular
     * region of pixels from its source Image as specified by the x, y,
     * w, and h parameters.
     * @param x the x location of the top of the rectangle to be extracted
     * @param y the y location of the top of the rectangle to be extracted
     * @param w the width of the rectangle to be extracted
     * @param h the height of the rectangle to be extracted
     */
    public CropImageFilter(int x, int y, int w, int h) {
        cropX = x;
        cropY = y;
        cropW = w;
        cropH = h;
    }

    
Passes along the properties from the source object after adding a property indicating the cropped region. This method invokes super.setProperties, which might result in additional properties being added. 
 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
/**
     * Passes along  the properties from the source object after adding a
     * property indicating the cropped region.
     * This method invokes {@code super.setProperties},
     * which might result in additional properties being added.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose pixels
     * are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     */
    public void setProperties(Hashtable<?,?> props) {
        @SuppressWarnings("unchecked")
        Hashtable<Object,Object> p = (Hashtable<Object,Object>)props.clone();
        p.put("croprect", new Rectangle(cropX, cropY, cropW, cropH));
        super.setProperties(p);
    }

    
Override the source image's dimensions and pass the dimensions
of the rectangular cropped region to the ImageConsumer.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
See Also:
/**
     * Override the source image's dimensions and pass the dimensions
     * of the rectangular cropped region to the ImageConsumer.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose
     * pixels are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     * @see ImageConsumer
     */
    public void setDimensions(int w, int h) {
        consumer.setDimensions(cropW, cropH);
    }

    
Determine whether the delivered byte pixels intersect the region to
be extracted and passes through only that subset of pixels that
appear in the output region.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
/**
     * Determine whether the delivered byte pixels intersect the region to
     * be extracted and passes through only that subset of pixels that
     * appear in the output region.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose
     * pixels are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     */
    public void setPixels(int x, int y, int w, int h,
                          ColorModel model, byte pixels[], int off,
                          int scansize) {
        int x1 = x;
        if (x1 < cropX) {
            x1 = cropX;
        }
    int x2 = addWithoutOverflow(x, w);
        if (x2 > cropX + cropW) {
            x2 = cropX + cropW;
        }
        int y1 = y;
        if (y1 < cropY) {
            y1 = cropY;
        }

    int y2 = addWithoutOverflow(y, h);
        if (y2 > cropY + cropH) {
            y2 = cropY + cropH;
        }
        if (x1 >= x2 || y1 >= y2) {
            return;
        }
        consumer.setPixels(x1 - cropX, y1 - cropY, (x2 - x1), (y2 - y1),
                           model, pixels,
                           off + (y1 - y) * scansize + (x1 - x), scansize);
    }

    
Determine if the delivered int pixels intersect the region to
be extracted and pass through only that subset of pixels that
appear in the output region.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
/**
     * Determine if the delivered int pixels intersect the region to
     * be extracted and pass through only that subset of pixels that
     * appear in the output region.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose
     * pixels are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     */
    public void setPixels(int x, int y, int w, int h,
                          ColorModel model, int pixels[], int off,
                          int scansize) {
        int x1 = x;
        if (x1 < cropX) {
            x1 = cropX;
        }
    int x2 = addWithoutOverflow(x, w);
        if (x2 > cropX + cropW) {
            x2 = cropX + cropW;
        }
        int y1 = y;
        if (y1 < cropY) {
            y1 = cropY;
        }

    int y2 = addWithoutOverflow(y, h);
        if (y2 > cropY + cropH) {
            y2 = cropY + cropH;
        }
        if (x1 >= x2 || y1 >= y2) {
            return;
        }
        consumer.setPixels(x1 - cropX, y1 - cropY, (x2 - x1), (y2 - y1),
                           model, pixels,
                           off + (y1 - y) * scansize + (x1 - x), scansize);
    }

    //check for potential overflow (see bug 4801285)
    private int addWithoutOverflow(int x, int w) {
        int x2 = x + w;
        if ( x > 0 && w > 0 && x2 < 0 ) {
            x2 = Integer.MAX_VALUE;
        } else if( x < 0 && w < 0 && x2 > 0 ) {
            x2 = Integer.MIN_VALUE;
        }
        return x2;
    }
}