java - 矩形内 BufferedImage 的渲染部分

Question

我目前正在尝试仅绘制 BufferedImage 的一部分，该部分位于动态矩形的边界内。图像发生移动，因此矩形中图像的大小发生变化。

视觉描绘:

目前，这就是我所拥有的，它对于低分辨率图像效果很好。但如果我放大小 map ，这会变得非常低效并导致滞后

private BufferedImage extractPixels() {
    int[] imagePixels = new int[scaledImage.getWidth() * scaledImage.getHeight()];
    scaledImage.getRGB(0, 0, scaledImage.getWidth(), scaledImage.getHeight(), imagePixels,
            0, scaledImage.getWidth());
    int maxX = 0, maxY = 0;
    boolean first = false;
    for (int y = 0; y < scaledImage.getHeight(); y++) {
        for (int x = 0; x < scaledImage.getWidth(); x++) {
            int px = (int)(this.x + x);
            int py = (int)(this.y + y);
            if (viewingArea.contains(px, py)) {
                if (x > maxX) maxX = x;
                if (y > maxY) maxY = y;
                if (!first) {
                    imageX = x;
                    imageY = y;
                    first = true;
                }
            }
        }
    }
    int xCount = maxX - imageX;
    int yCount = maxY - imageY;
    if (imageX < 0 || imageX > scaledImage.getWidth() || imageX + xCount > scaledImage.getWidth()) return null;
    if (imageY < 0 || imageY > scaledImage.getHeight() || imageY + yCount > scaledImage.getHeight()) return null;
    return scaledImage.getSubimage(imageX, imageY, xCount, yCount);
}

在渲染循环中:

public void Render(PixelRenderer renderer) {
    BufferedImage image = extractPixels();
    if (image != null) renderer.renderImage(image, x + imageX, y + imageY);
}

有没有一种方法可以更有效地做到这一点，以便重新缩放对性能的影响较小？

Answer 1

通过计算图像应从何处生成子图像以及子图像的大小取决于主图像的位置来修复。

private BufferedImage extractPixels() {
    double xp = viewingArea.x - this.x;
    double yp = viewingArea.y - this.y;
    double iw = viewingArea.width;
    double ih = viewingArea.height;

    int rightBound = scaledImage.getWidth() - viewingArea.width;
    int bottomBound = scaledImage.getHeight() - viewingArea.height;

    if (xp < 0) {
        xp = 0;
        iw = viewingArea.width - (this.x - viewingArea.x);
        imageX = viewingArea.x + (viewingArea.width - (int)iw);
    } else if (xp >= 0 && xp < rightBound) {
        xp -= dx;
        iw -= dx;
        imageX = viewingArea.x;
    }
    if (xp >= rightBound) {
        iw = viewingArea.width - ((int)xp - (scaledImage.getWidth() - viewingArea.width));
        imageX = viewingArea.x;
    }

    if (yp < 0) {
        yp = 0;
        ih = viewingArea.height - (this.y - viewingArea.y);
        imageY = viewingArea.x + (viewingArea.height - (int)ih);
    } else if (yp >= 0 && yp < bottomBound) {
        yp -= dy;
        ih -= dy;
        imageY = viewingArea.y;
    }
    if (yp >= bottomBound) {
        ih = viewingArea.height - ((int)yp - (scaledImage.getHeight() - viewingArea.height));
        imageY = viewingArea.y;
    }

    if (iw < 0) iw = Math.abs(iw);
    if (ih < 0) ih = Math.abs(ih);
    if (xp < 0) xp = Math.abs(xp);
    if (yp < 0) yp = Math.abs(yp);

    BufferedImage result = new BufferedImage((int)iw, (int)ih, BufferedImage.TYPE_INT_RGB);

    try {
        result = scaledImage.getSubimage((int)xp, (int)yp, (int)iw, (int)ih);
    } catch (Exception e) {
        //TODO: Log to game engine something bad has happened
        e.printStackTrace();
    }

    return result;
}