test4.java

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class LayeredCrosshatchDemo {

    // Suppose we have enumerated density levels
    public enum DensityLevel {
        LOW,
        MEDIUM,
        HIGH
    }

    // A region’s data structure: set of pixel coordinates + which density it should be
    public static class Region {
        private Set<Point> pixelCoordinates;
        private DensityLevel densityLevel;

        public Region(Set<Point> pixels, DensityLevel densityLevel) {
            this.pixelCoordinates = pixels;
            this.densityLevel = densityLevel;
        }

        public Set<Point> getPixelCoordinates() {
            return pixelCoordinates;
        }

        public DensityLevel getDensityLevel() {
            return densityLevel;
        }
    }

    public static void main(String[] args) {
        int width = 600;
        int height = 400;

        // 1) Generate 3 separate "layer" images, one for each density
        //    All have ARGB so we can do transparency (alpha)
        BufferedImage layerLow    = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        BufferedImage layerMedium = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        BufferedImage layerHigh   = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);

        // 2) For each layer, fill with crosshatching at the appropriate spacing
        //    but fill the entire image with that pattern. We'll mask out unwanted areas later.
        drawCrosshatchesFull(layerLow,    15); // bigger spacing => sparser
        drawCrosshatchesFull(layerMedium, 8);
        drawCrosshatchesFull(layerHigh,   4);  // smaller spacing => denser

        // 3) Construct some example Region data
        Region regionA = makeRegion( 50,50, 100,60, DensityLevel.LOW);  // a rectangle for demonstration
        Region regionB = makeRegion(150,80,  80,50, DensityLevel.MEDIUM);
        Region regionC = makeRegion(300,120, 50, 60, DensityLevel.HIGH);
        List<Region> allRegions = List.of(regionA, regionB, regionC);

        // 4) For each region, we "unmask" the corresponding layer in its pixelCoordinates
        //    and set the rest to transparent. Or equivalently, we can set all pixels
        //    outside the region to 0 alpha in that layer.
        //    We'll do it by clearing the alpha outside of the region.
        maskLayersByRegion(allRegions, layerLow, layerMedium, layerHigh);

        // 5) Finally, create the final image with white background (or anything).
        BufferedImage finalImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D gFinal = finalImage.createGraphics();
        try {
            // White background
            gFinal.setColor(Color.WHITE);
            gFinal.fillRect(0, 0, width, height);

            // Draw each layer on top
            gFinal.drawImage(layerLow,    0, 0, null);
            gFinal.drawImage(layerMedium, 0, 0, null);
            gFinal.drawImage(layerHigh,   0, 0, null);
            
            // At this point, finalImage is complete. 
            // You can write it out or display it, e.g.:
            // ImageIO.write(finalImage, "PNG", new File("crosshatchedResult.png"));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            gFinal.dispose();
        }
    }

    /**
     * Draws crosshatches across the entire buffered image at the given spacing.
     * We'll assume black crosshatches on a transparent background. 
     * (i.e., everything else is 0 alpha).
     */
    private static void drawCrosshatchesFull(BufferedImage layer, int spacing) {
        int width = layer.getWidth();
        int height = layer.getHeight();

        Graphics2D g = layer.createGraphics();
        try {
            // Start with a fully transparent background
            g.setComposite(AlphaComposite.Clear);
            g.fillRect(0, 0, width, height);

            // Now switch to "SrcOver" so we can draw the lines in black
            g.setComposite(AlphaComposite.SrcOver);

            // Optionally set stroke to 1 pixel or thinner
            g.setStroke(new BasicStroke(1.0f));
            g.setColor(Color.BLACK);

            // For "/" diagonals
            for (int y = 0; y <= height; y += spacing) {
                drawOneDiagonalLineFull(g, 0, y, width, height, +1);
            }
            for (int x = 0; x <= width; x += spacing) {
                drawOneDiagonalLineFull(g, x, height, width, height, +1);
            }

            // For "\" diagonals
            for (int y = 0; y <= height; y += spacing) {
                drawOneDiagonalLineFull(g, 0, y, width, height, -1);
            }
            for (int x = 0; x <= width; x += spacing) {
                drawOneDiagonalLineFull(g, x, 0, width, height, -1);
            }
        } finally {
            g.dispose();
        }
    }

    /**
     * Draws one diagonal line from (startX, startY) in either "/" or "\" direction
     * all the way across the image. 
     */
    private static void drawOneDiagonalLineFull(Graphics2D g,
                                                int startX, int startY,
                                                int width, int height,
                                                int direction) {
        // direction = +1 => "/"
        // direction = -1 => "\"

        // We'll step in increments of 1 pixel until we're out of the image bounds
        int x = startX;
        int y = startY;
        int stepCount = width + height; // worst case diagonal length

        for (int i = 0; i < stepCount; i++) {
            // If out of bounds, break
            if (x < 0 || x >= width || y < 0 || y >= height) {
                break;
            }
            // Draw a tiny line from (x, y) to (x, y). 
            // Actually, we can just do g.drawLine(x, y, x, y).
            g.drawLine(x, y, x, y);

            // Move diagonally 
            x += 1 * direction;   // +/-1 in the x-direction
            y -= 1;               // always up 1 in y for "/"
                                 // or if direction=-1 => that changes the diagonal slope
                                 // (this is the same logic we used before, just in "full layer" context)
        }
    }

    /**
     * For each region in the list, keep the crosshatching in the appropriate layer 
     * within region pixels, and set everything else to transparent in that layer.
     */
    private static void maskLayersByRegion(List<Region> regions,
                                           BufferedImage layerLow,
                                           BufferedImage layerMedium,
                                           BufferedImage layerHigh) {
        // We'll do a quick pass creating a large sets of region pixels 
        // for each density.
        Set<Point> lowSet    = new HashSet<>();
        Set<Point> mediumSet = new HashSet<>();
        Set<Point> highSet   = new HashSet<>();

        for (Region region : regions) {
            switch (region.getDensityLevel()) {
                case LOW ->    lowSet.addAll(region.getPixelCoordinates());
                case MEDIUM -> mediumSet.addAll(region.getPixelCoordinates());
                case HIGH ->   highSet.addAll(region.getPixelCoordinates());
            }
        }

        // Now we’ll mask each layer by iterating over every pixel.
        maskLayer(layerLow,    lowSet);
        maskLayer(layerMedium, mediumSet);
        maskLayer(layerHigh,   highSet);
    }

    /**
     * Sets all pixels *not in the given set* to fully transparent (ARGB=0)
     * so that only region pixels remain.
     */
    private static void maskLayer(BufferedImage layer, Set<Point> regionPoints) {
        int width = layer.getWidth();
        int height = layer.getHeight();

        // For quick membership checks:
        // regionPoints is a set of (x,y). 
        // If you have extremely large images, you might prefer a scanline approach. 
        // But let's keep it straightforward for demonstration.
        for (int y = 0; y < height; y++) {
            for (int x = 0; x < width; x++) {
                if (!regionPoints.contains(new Point(x, y))) {
                    // Set alpha to 0
                    layer.setRGB(x, y, 0x00000000);
                }
            }
        }
    }

    /**
     * Helper method to create a simple rectangular region.
     * This is just for the demo; in your code, you'd have real shapes.
     */
    private static Region makeRegion(int startX, int startY, int w, int h, DensityLevel density) {
        Set<Point> coords = new HashSet<>();
        for (int y = startY; y < startY + h; y++) {
            for (int x = startX; x < startX + w; x++) {
                coords.add(new Point(x, y));
            }
        }
        return new Region(coords, density);
    }
}

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