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Testing Image Color Conversion Utilities in Stirling-PDF

This test suite validates the image processing utilities in Stirling-PDF, focusing on color conversion functionality. The tests verify different color transformation methods including greyscale, black/white, and full color conversions with proper image type validation.

Test Coverage Overview

The test suite provides comprehensive coverage of image color conversion operations.

Key areas tested include:

Greyscale conversion with pixel value validation
Black and white binary conversion
Full color preservation
Invalid color type handling

Edge cases cover input validation and color space integrity verification.

Implementation Analysis

The testing approach utilizes JUnit 5 framework with systematic verification of image properties and pixel-level assertions. The implementation follows a pattern of creating source images, applying conversions, and validating both image attributes and color values using BufferedImage manipulation.

Framework features leverage @Test annotations and assertion methods for precise validation.

Technical Details

Testing tools and components:

JUnit Jupiter test framework
Java AWT and BufferedImage classes
Custom utility methods for image manipulation
RGB color space validation
Image type constants (TYPE_BYTE_GRAY, TYPE_BYTE_BINARY)

Best Practices Demonstrated

The test suite exemplifies robust testing practices through isolated test methods, comprehensive assertions, and proper setup helpers.

Notable practices include:

Systematic validation of image properties
Pixel-level verification
Helper method extraction for common operations
Clear test method naming conventions
Proper error case handling

stirling-tools/stirling-pdf

src/test/java/stirling/software/SPDF/utils/ImageProcessingUtilsTest.java

            
package stirling.software.SPDF.utils;

import org.junit.jupiter.api.Test;

import java.awt.*;
import java.awt.image.BufferedImage;

import static org.junit.jupiter.api.Assertions.*;

public class ImageProcessingUtilsTest {

    @Test
    void testConvertColorTypeToGreyscale() {
        BufferedImage sourceImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
        fillImageWithColor(sourceImage, Color.RED);

        BufferedImage convertedImage = ImageProcessingUtils.convertColorType(sourceImage, "greyscale");

        assertNotNull(convertedImage);
        assertEquals(BufferedImage.TYPE_BYTE_GRAY, convertedImage.getType());
        assertEquals(sourceImage.getWidth(), convertedImage.getWidth());
        assertEquals(sourceImage.getHeight(), convertedImage.getHeight());

        // Check if a pixel is correctly converted to greyscale
        Color grey = new Color(convertedImage.getRGB(0, 0));
        assertEquals(grey.getRed(), grey.getGreen());
        assertEquals(grey.getGreen(), grey.getBlue());
    }

    @Test
    void testConvertColorTypeToBlackWhite() {
        BufferedImage sourceImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
        fillImageWithColor(sourceImage, Color.RED);

        BufferedImage convertedImage = ImageProcessingUtils.convertColorType(sourceImage, "blackwhite");

        assertNotNull(convertedImage);
        assertEquals(BufferedImage.TYPE_BYTE_BINARY, convertedImage.getType());
        assertEquals(sourceImage.getWidth(), convertedImage.getWidth());
        assertEquals(sourceImage.getHeight(), convertedImage.getHeight());

        // Check if a pixel is converted correctly (binary image will be either black or white)
        int rgb = convertedImage.getRGB(0, 0);
        assertTrue(rgb == Color.BLACK.getRGB() || rgb == Color.WHITE.getRGB());
    }

    @Test
    void testConvertColorTypeToFullColor() {
        BufferedImage sourceImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
        fillImageWithColor(sourceImage, Color.RED);

        BufferedImage convertedImage = ImageProcessingUtils.convertColorType(sourceImage, "fullcolor");

        assertNotNull(convertedImage);
        assertEquals(sourceImage, convertedImage);
    }

    @Test
    void testConvertColorTypeInvalid() {
        BufferedImage sourceImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
        fillImageWithColor(sourceImage, Color.RED);

        BufferedImage convertedImage = ImageProcessingUtils.convertColorType(sourceImage, "invalidtype");

        assertNotNull(convertedImage);
        assertEquals(sourceImage, convertedImage);
    }

    private void fillImageWithColor(BufferedImage image, Color color) {
        for (int y = 0; y < image.getHeight(); y++) {
            for (int x = 0; x < image.getWidth(); x++) {
                image.setRGB(x, y, color.getRGB());
            }
        }
    }
}