TheAlgorithms/Java · error · IllegalArgumentException

imageHeight should be greater than zero

Error message

imageHeight should be greater than zero

What it means

Thrown by Mandelbrot.getImage when imageHeight <= 0. The method allocates a BufferedImage of imageWidth x imageHeight and uses imageHeight in the figureHeight computation, so a non-positive height produces a degenerate image and is rejected before allocation.

Source

Thrown at src/main/java/com/thealgorithms/others/Mandelbrot.java:81

     * area of the Mandelbrot set is roughly between "-1.5 < x < 0.5" and "-1 <
     * y < 1" in the figure-coordinates.
     *
     * @param imageWidth The width of the rendered image.
     * @param imageHeight The height of the rendered image.
     * @param figureCenterX The x-coordinate of the center of the figure.
     * @param figureCenterY The y-coordinate of the center of the figure.
     * @param figureWidth The width of the figure.
     * @param maxStep Maximum number of steps to check for divergent behavior.
     * @param useDistanceColorCoding Render in color or black and white.
     * @return The image of the rendered Mandelbrot set.
     */
    public static BufferedImage getImage(int imageWidth, int imageHeight, double figureCenterX, double figureCenterY, double figureWidth, int maxStep, boolean useDistanceColorCoding) {
        if (imageWidth <= 0) {
            throw new IllegalArgumentException("imageWidth should be greater than zero");
        }

        if (imageHeight <= 0) {
            throw new IllegalArgumentException("imageHeight should be greater than zero");
        }

        if (maxStep <= 0) {
            throw new IllegalArgumentException("maxStep should be greater than zero");
        }

        BufferedImage image = new BufferedImage(imageWidth, imageHeight, BufferedImage.TYPE_INT_RGB);
        double figureHeight = figureWidth / imageWidth * imageHeight;

        // loop through the image-coordinates
        for (int imageX = 0; imageX < imageWidth; imageX++) {
            for (int imageY = 0; imageY < imageHeight; imageY++) {
                // determine the figure-coordinates based on the image-coordinates
                double figureX = figureCenterX + ((double) imageX / imageWidth - 0.5) * figureWidth;
                double figureY = figureCenterY + ((double) imageY / imageHeight - 0.5) * figureHeight;

                double distance = getDistance(figureX, figureY, maxStep);

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Provide a positive imageHeight (e.g. 600) when calling getImage.
2. Default height to a positive value when the source is missing or zero.
3. Validate both dimensions at the input boundary before invoking.
4. Make sure aspect-ratio computations cannot yield 0.

Example fix

// before
BufferedImage img = Mandelbrot.getImage(width, height, cx, cy, fw, maxStep, color); // height may be 0

// after
int h = height > 0 ? height : 600;
BufferedImage img = Mandelbrot.getImage(width, h, cx, cy, fw, maxStep, color);

if (imageHeight <= 0) imageHeight = 600;
BufferedImage img = Mandelbrot.getImage(imageWidth, imageHeight, cx, cy, fw, maxStep, color);

public static boolean isPositiveDimension(int dim) {
    return dim > 0;
}

try {
    img = Mandelbrot.getImage(w, h, cx, cy, fw, maxStep, color);
} catch (IllegalArgumentException e) {
    img = Mandelbrot.getImage(w, 600, cx, cy, fw, maxStep, color);
}

When it happens

Trigger: Calling getImage(..., imageHeight, ...) with imageHeight of 0 or negative; height read from a config/CLI argument that defaults to 0 when unset.

Common situations: Unset height parameter defaulting to 0; CLI parsing returning 0; portrait/landscape auto-calc producing 0 before a layout pass; negative height from subtraction.

Related errors

• imageWidth should be greater than zero
• imageWidth should be greater than zero
• maxStep should be greater than zero
• Input '{input}' contains not only digits
• Position must be between 0 and {array.length}

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/88c8eaf3dba18550. Report an issue: GitHub.