如何在 PDF 渲染器中反转参考底图颜色

问：

我目前正在使用 Apache PDFBox 3.0.0 在 Java 中实现 PDF 渲染器，我想添加使用 XOR（独占 OR）模式绘制 PDF 元素（如字符串、矩形和线条）的功能，以反转基础元素的颜色。此效果通常用于突出显示或反转图形。

例：

PDFRenderer：

public class PDFRenderer {
    private PDDocument pdDocument;
    private PDPageContentStream contentStream;

    private float originY;
    private float originX;

    public PDFRenderer() {
        this.pdDocument = new PDDocument();

        PDPage pdPage = new PDPage();
        this.pdDocument.addPage(pdPage);

        try {
            this.contentStream = new PDPageContentStream(pdDocument, pdPage, AppendMode.APPEND, false, false);
        } catch (IOException e) {
            e.printStackTrace();
        }

        originY = pdPage.getMediaBox().getHeight();
        originX = 0;
    }

    /**
     * Draws a string on the canvas.
     *
     * @param text The text to draw.
     * @param x The x-coordinate of the top-left corner of the text.
     * @param y The y-coordinate of the top-left corner of the text.
     * @param width The width of the text box.
     * @param height The height of the text box.
     * @param color The color of the text.
     * @param font The font to use.
     */
    public void drawString(String text, int x, int y, int width, int height, CustomColor color, CustomFont font) {
        try {
            setStrokingColor(color);

            int fontHeight = Math.round((font.getFont().getFontDescriptor().getCapHeight()) / 1000 * height);
            float textWidth = font.getFont().getStringWidth(text) / 1000 * height;

            contentStream.setFont(font.getFont(), height);
            contentStream.setHorizontalScaling(100 + width);
            contentStream.beginText();
            contentStream.newLineAtOffset(originX + x, originY - fontHeight - y);
            contentStream.showText(text);
            contentStream.endText();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Draws a rectangle on the canvas.
     *
     * @param x The x-coordinate of the top-left corner of the rectangle.
     * @param y The y-coordinate of the top-left corner of the rectangle.
     * @param width The width of the rectangle.
     * @param height The height of the rectangle.
     * @param borderThickness The thickness of the rectangle's border.
     * @param color The color of the rectangle.
     * @param degreeOfCornerRounding The degree of corner rounding for the rectangle accepted are values from 1 to 8.
     * @param colorInverted Indicates if the rectangle color is inverted.
     */
    public void drawRectangle(int x, int y, int width, int height, int borderThickness, CustomColor color, int degreeOfCornerRounding, boolean colorInverted) {
        try {
            setStrokingColor(color);

            if (borderThickness > width / 2) {
                borderThickness = width / 2;
            } else if (borderThickness > height / 2) {
                borderThickness = height / 2;
            }

            float borderOffset = borderThickness / 2.0f;
            float adjustedX = originX + x + borderOffset;
            float adjustedY = originY - y - height + borderOffset;
            float adjustedWidth = width - borderThickness;
            float adjustedHeight = height - borderThickness;

            contentStream.setLineWidth(borderThickness);

            contentStream.addRect(adjustedX, adjustedY, adjustedWidth, adjustedHeight);

            contentStream.stroke();
        } catch (NumberFormatException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Draws a line on the canvas.
     *
     * @param x The x-coordinate of the starting point of the line.
     * @param y The y-coordinate of the starting point of the line.
     * @param width The horizontal length of the line.
     * @param height The vertical length of the line.
     * @param thickness The thickness of the line.
     * @param color The color of the line.
     */
    public void drawLine(int x, int y, int width, int height, int thickness, CustomColor color) {
        try {
            setStrokingColor(color);

            float adjustedX = originX + x;
            float adjustedY = originY - y;

            contentStream.setLineWidth(thickness);
            contentStream.moveTo(adjustedX, adjustedY);
            contentStream.lineTo(adjustedX + width, adjustedY - height);
            contentStream.stroke();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void setStrokingColor(CustomColor color) throws NumberFormatException, IOException {
        contentStream.setStrokingColor(
                Integer.parseInt(color.getHexadecimal().substring(1, 3), 16) / 255f,
                Integer.parseInt(color.getHexadecimal().substring(3, 5), 16) / 255f,
                Integer.parseInt(color.getHexadecimal().substring(5, 7), 16) / 255f
        );
    }
}

用法：

PDFRenderer pdfRenderer = new PDFRenderer();

pdfRenderer.drawRectangle(50, 50, 100, 100, 100, CustomColortim.BLACK, 2);
pdfRenderer.drawLine(50, 500, 700, 3, 3, CustomColor.BLACK);
pdfRenderer.drawString("Hello, World!", 220, 195, 100, 30, CustomColor.BLACK, CustomFont.A);

具体问题

1. 在 Java 中使用 Apache PDFBox 3.0.0 绘制矩形、线条和文本等 PDF 元素时，如何修改 PDFRenderer 类以实现异或颜色反转？

2. PDFBox 中是否有任何内置函数或方法支持用于颜色处理的 XOR 模式？

3. 您能否提供在此上下文中实现 XOR 颜色反转的代码示例或建议？