使用 Java 缩放图像会产生黑色空间

Question

我编写了以下函数来缩小图像。但是，虽然缩放有效，但生成的图像始终是方形图像，并且在图像的底部或右侧有一个黑色空间。我在这里做错了什么？

private BufferedImage scaleImageTo(BufferedImage image, int width, int height) throws Exception {
    // Fetch the width and height of the source image, ...
    int srcWidth = image.getWidth();
    int srcHeight = image.getHeight();

    // ... verify that it is larger than the target image ...
    if (srcWidth < width && srcHeight < height) {
        throw new Exception();
    }

    // ... and setup the target image with the same dimensions.
    BufferedImage scaledImage;
    if (image.getType() == BufferedImage.TYPE_CUSTOM) {
        scaledImage = new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
    } else {
        scaledImage = new BufferedImage(width, height, image.getType());
    }

    // Calculate the scale parameter.
    double scale = 1;
    if (srcWidth - width >= srcHeight - height) {
        scale = ((double) width) / srcWidth;
    } else {
        scale = ((double) height) / srcHeight;
    }

    // Setup the scaling transformation ...
    AffineTransform at = new AffineTransform();
    at.scale(scale, scale);

    // ... and the transformation interpolation type.
    AffineTransformOp scaleOp = new AffineTransformOp(at, AffineTransformOp.TYPE_BILINEAR);

    // Generate the scaled image  ... 
    scaledImage = scaleOp.filter(image, scaledImage);

    // ... and return it.
    return scaledImage;
}

Answer 1

您始终在 x 和 y 方向使用相同的比例因子。

虽然您可以通过指定两个这样的比例因子来解决此问题

double scaleX = (double) width / srcWidth;
double scaleY = (double) height / srcHeight;
AffineTransform at = new AffineTransform();
at.scale(scaleX, scaleY);

我想知道你为什么这样做。仅仅创建一个缩放版本的图像通常是相当容易的......：

private static BufferedImage scaleImageTo(
    BufferedImage image, int width, int height) 
{
    BufferedImage scaledImage =
        new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = scaledImage.createGraphics();
    g.setRenderingHint(
        RenderingHints.KEY_INTERPOLATION, 
        RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g.drawImage(image, 0, 0, width, height, null);
    g.dispose();
    return scaledImage;
}