如何像imageview一样裁剪位图中心? [英] How to crop Bitmap Center like imageview?

问题描述

可能重复:
如何在android中裁剪解析后的图像?

如何以与 Android 的 ImageView 相同的方式进行裁剪

How does one crop the same way as Androids ImageView is doing

android:scaleType="centerCrop"

推荐答案

你的问题有点缺乏关于你想要完成什么的信息，但我猜你有一个位图并且想要将它缩放到一个新的大小缩放应该在 ImageViews 中使用centerCrop".

Your question is a bit short of information on what you want to accomplish, but I guess you have a Bitmap and want to scale that to a new size and that the scaling should be done as "centerCrop" works for ImageViews.

来自文档

均匀缩放图像(保持图像的纵横比)，以便图像的两个尺寸(宽度和高度)将等于或大于视图的相应尺寸(减去填充).

Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or larger than the corresponding dimension of the view (minus padding).

据我所知，没有单一的方法可以做到这一点(如果我错了，请纠正我)，但您可以编写自己的方法来做到这一点.以下方法计算如何将原始位图缩放到新大小并在生成的位图中居中绘制.

As far as I know, there is no one-liner to do this (please correct me, if I'm wrong), but you could write your own method to do it. The following method calculates how to scale the original bitmap to the new size and draw it centered in the resulting Bitmap.

希望对你有帮助！

public Bitmap scaleCenterCrop(Bitmap source, int newHeight, int newWidth) {
    int sourceWidth = source.getWidth();
    int sourceHeight = source.getHeight();

    // Compute the scaling factors to fit the new height and width, respectively.
    // To cover the final image, the final scaling will be the bigger 
    // of these two.
    float xScale = (float) newWidth / sourceWidth;
    float yScale = (float) newHeight / sourceHeight;
    float scale = Math.max(xScale, yScale);

    // Now get the size of the source bitmap when scaled
    float scaledWidth = scale * sourceWidth;
    float scaledHeight = scale * sourceHeight;

    // Let's find out the upper left coordinates if the scaled bitmap
    // should be centered in the new size give by the parameters
    float left = (newWidth - scaledWidth) / 2;
    float top = (newHeight - scaledHeight) / 2;

    // The target rectangle for the new, scaled version of the source bitmap will now
    // be
    RectF targetRect = new RectF(left, top, left + scaledWidth, top + scaledHeight);

    // Finally, we create a new bitmap of the specified size and draw our new,
    // scaled bitmap onto it.
    Bitmap dest = Bitmap.createBitmap(newWidth, newHeight, source.getConfig());
    Canvas canvas = new Canvas(dest);
    canvas.drawBitmap(source, null, targetRect, null);

    return dest;
}

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