Java文檔圖像縮放和旋轉

Question

我有不同尺寸的文檔圖像，並且希望能夠以以下方式（標准“旋轉”和“縮放”邏輯）有效縮放和旋轉它們。 我該怎么做？

圖像的高度為H像素，寬度為W像素。 最初，它應該縮放到600像素寬。 每次旋轉時，面板的寬度和高度應互換，縮放的圖像應旋轉90度。 每次縮放時，圖像應按“比例”比例縮放。

到目前為止，這是我在BufferedImage img上嘗試過的方法...生成的BufferedImage縮放並旋轉但不平移（在旋轉90度后居中於面板頂部）：

double scale = zoom * 600.0 / img.getWidth();
rotation = (rotation + degrees) % 360;
int scaledWidth = (int)(scale * img.getWidth());
int scaledHeight = (int)(scale * img.getHeight());
BufferedImage bufferedImage = new BufferedImage(scaledWidth, scaledHeight, img.getType());
if (rotation % 180 == 0)
    bufferedImage = new BufferedImage(scaledWidth, scaledHeight, img.getType());
else
    bufferedImage = new BufferedImage(scaledHeight, scaledWidth, img.getType());

AffineTransform transform = AffineTransform.getRotateInstance(Math.toRadians(rotation), scaledWidth/2, scaledHeight/2);
transform.scale(scale, scale);
AffineTransformOp operation = new AffineTransformOp(transform, AffineTransformOp.TYPE_BILINEAR);
scaledImage = operation.filter(img, bufferedImage);
imagePanel.setPreferredSize(new Dimension(bufferedImage.getWidth(), bufferedImage.getHeight()));

Answer 1

啊哈！ 關鍵（JavaDoc令人困惑）是意識到在AffineTransform ， rotate()和其他方法可以轉換矩陣，而不是圖像！ 以下代碼可以自動運行！

/**
 * Transforms the image efficiently without losing image quality.
 * Scales the image to a width of (600 * scale) pixels, rotates the image,
 * and translates (moves) the image to recenter it if rotated 90 or 270 degrees.
 */
protected BufferedImage transformImage(BufferedImage image)
{
    int scaledWidth = (int)(scale * image.getWidth());
    int scaledHeight = (int)(scale * image.getHeight());

    // Methods AffineTransform.rotate(), AffineTransform.scale() and AffineTransform.translate()
    // transform AffineTransform's transformation matrix to multiply with the buffered image.
    // Therefore those methods are called in a counterintuitive sequence.
    AffineTransform transform;
    if (rotation % 180 == 0)
    {
        // First scale and second rotate image
        transform = AffineTransform.getRotateInstance(Math.toRadians(rotation), scaledWidth/2, scaledHeight/2);
        transform.scale(scale, scale);
    }
    else
    {
        // First scale, second rotate, and third translate image
        transform = AffineTransform.getTranslateInstance((scaledHeight-scaledWidth)/2, (scaledWidth-scaledHeight)/2);
        transform.rotate(Math.toRadians(rotation), scaledWidth/2, scaledHeight/2);
        transform.scale(scale, scale);
    }
    AffineTransformOp operation = new AffineTransformOp(transform, AffineTransformOp.TYPE_BICUBIC);
    BufferedImage transformedImage = operation.createCompatibleDestImage(image, image.getColorModel());
    return operation.filter(image, transformedImage);
}