Java 不固定长度文本的指定宽度与自适应图片绘制实战

公共方法准备

为了美观，我们为每个条目生成均匀分布的颜色。这里利用 HSV 色环原理生成可区分颜色，并将 Color 对象转为十六进制字符串备用。

/**
 * - 将 color 转十六进制字符串
 * @param color
 * @return
 */
public static String Color2String(Color color) {
    // 获取 RGB 颜色值，格式为 0x00RRGGBB
    int rgb = color.getRGB();
    // 将 RGB 转换为十六进制字符串，去掉前两位的透明度部分（如果是纯不透明颜色）
    String hexColor = "#" + Integer.toHexString(rgb & 0xffffff);
    return hexColor;
}

// 生成可区分颜色（HSV 色环均匀分布）
private static Color[] generateDistinctColors(int count) {
    Color[] colors = new Color[count];
    float goldenRatio = 0.618033988749895f; // 黄金分割比例
    float saturation = 0.8f; // 饱和度
    float brightness = 0.9f; // 亮度
    for (int i = 0; i < count; i++) {
        float hue = (i * goldenRatio) % 1.0f;
        colors[i] = Color.getHSBColor(hue, saturation, brightness);
    }
    return colors;
}

指定宽度生成实现

按指定宽度生成的关键在于先计算好布局参数，再统一绘制。由于宽度固定而文字不定，必须处理文本截断逻辑。

// 固定总宽度模式
public static BufferedImage createFixedColumnsImage(String[] texts, int columns, int totalWidth, Font font, int padding, int columnSpacing, int rowSpacing) {
    BufferedImage tempImg = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
    Graphics2D tempG = tempImg.createGraphics();
    tempG.setFont(font);
    FontMetrics fm = tempG.getFontMetrics();
    final int RECT_SIZE = 10;
    final int ENTRY_SPACING = 5;
    
    // 生成颜色序列
    Color[] colors = generateDistinctColors(texts.length);
    
    // 计算列宽
    int availableWidth = totalWidth - padding * 2 - (columns - 1) * columnSpacing;
    int columnWidth = availableWidth / columns;
    int textMaxWidth = columnWidth - RECT_SIZE - ENTRY_SPACING;
    
    // 处理文本，超长截断
    List<String> processedTexts = new ArrayList<>();
    for (String text : texts) {
        processedTexts.add(truncateText(text, textMaxWidth, fm));
    }
    
    // 计算总高度
    int rows = (int) Math.ceil((double)texts.length / columns);
    int totalHeight = padding * 2 + rows * (fm.getHeight() + rowSpacing) - rowSpacing;
    
    // 创建图像
    BufferedImage image = new BufferedImage(totalWidth, totalHeight, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = image.createGraphics();
    setupGraphics(g, font); // 假设已配置抗锯齿等基础设置
    
    // 绘制背景
    g.setColor(Color.WHITE);
    g.fillRect(0, 0, totalWidth, totalHeight);
    
    // 绘制条目
    int yBase = padding + fm.getAscent();
    int[] columnX = new int[columns];
    for (int i = 0; i < columns; i++) {
        columnX[i] = padding + i * (columnWidth + columnSpacing);
    }
    
    for (int i = 0; i < processedTexts.size(); i++) {
        g.setColor(colors[i]);
        int col = i % columns;
        int row = i / columns;
        int y = yBase + row * (fm.getHeight() + rowSpacing);
        int rectY = y - fm.getAscent() + (fm.getHeight() - RECT_SIZE)/2;
        
        // 绘制矩形
        g.fillRect(columnX[col], rectY, RECT_SIZE, RECT_SIZE);
        // 绘制文本
        g.drawString(processedTexts.get(i), columnX[col] + RECT_SIZE + ENTRY_SPACING, y);
    }
    
    g.dispose();
    tempG.dispose();
    return image;
}

文本截断是这里的重点，确保不会超出预留空间：

private static String truncateText(String text, int maxWidth, FontMetrics fm) {
    if (fm.stringWidth(text) <= maxWidth) return text;
    int ellipsisWidth = fm.stringWidth("...");
    int availableWidth = maxWidth - ellipsisWidth;
    int length = text.length();
    while (length > 0 && fm.stringWidth(text.substring(0, length)) > availableWidth) {
        length--;
    }
    return length > 0 ? text.substring(0, length) + "..." : "";
}

调用示例：

// 生成固定宽度图片（400px 宽，2 列）
BufferedImage fixedImage = createFixedColumnsImage(
    demoTexts, 2, 400, new Font("宋体", Font.PLAIN, 12), 15, 20, 10
);
ImageIO.write(fixedImage, "PNG", new File("D:/fixed_columns_250420.png"));

指定列自适应生成

自适应模式下，宽度由内容决定。我们需要先遍历一遍数据算出最大列宽，再正式绘图。

// 自适应列宽模式
public static BufferedImage createAdaptiveColumnsImage(String[] texts, int columns, Font font, int padding, int columnSpacing, int rowSpacing) {
    BufferedImage tempImg = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
    Graphics2D tempG = tempImg.createGraphics();
    tempG.setFont(font);
    FontMetrics fm = tempG.getFontMetrics();
    final int RECT_SIZE = 10;
    final int ENTRY_SPACING = 5;
    
    // 图标与文字间距
    Color[] colors = generateDistinctColors(texts.length);
    int index = 0;
    for (String text : texts) {
        texts[index] = Color2String(colors[index]) + " " + text;
        index++;
    }
    
    // 计算列宽
    int[] columnWidths = new int[columns];
    for (int i = 0; i < texts.length; i++) {
        int col = i % columns;
        int width = RECT_SIZE + ENTRY_SPACING + fm.stringWidth(texts[i]);
        if (width > columnWidths[col]) {
            columnWidths[col] = width;
        }
    }
    
    // 计算总尺寸
    int totalWidth = padding * 2;
    for (int w : columnWidths) {
        totalWidth += w + columnSpacing;
    }
    totalWidth -= columnSpacing; // 最后一列不加间距
    
    int rows = (int) Math.ceil((double)texts.length / columns);
    int totalHeight = padding * 2 + rows * (fm.getHeight() + rowSpacing) - rowSpacing;
    
    // 创建图像
    BufferedImage image = new BufferedImage(totalWidth, totalHeight, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = image.createGraphics();
    setupGraphics(g, font);
    
    // 绘制背景
    g.setColor(Color.WHITE);
    g.fillRect(0, 0, totalWidth, totalHeight);
    
    // 绘制条目
    int x = padding;
    int yBase = padding + fm.getAscent();
    int[] columnX = new int[columns];
    for (int i = 0; i < columns; i++) {
        columnX[i] = x;
        x += columnWidths[i] + columnSpacing;
    }
    
    g.setColor(Color.RED);
    for (int i = 0; i < texts.length; i++) {
        g.setColor(colors[i]);
        int col = i % columns;
        int row = i / columns;
        int y = yBase + row * (fm.getHeight() + rowSpacing);
        int rectY = y - fm.getAscent() + (fm.getHeight() - RECT_SIZE)/2;
        
        // 绘制矩形
        g.fillRect(columnX[col], rectY, RECT_SIZE, RECT_SIZE);
        // 绘制文本
        g.drawString(texts[i], columnX[col] + RECT_SIZE + ENTRY_SPACING, y);
    }
    
    g.dispose();
    tempG.dispose();
    return image;
}

最终生成的结果图片如下：