如何获得大小完全相同的缩略图？

Question

Android 有一个 MediaStore.Images.Thumbnails.getThumbnail() 方法，它将返回任何图像的缩略图。但我注意到缩略图的大小仅限于 MICRO_KIND 和 MINI_KIND。如何获得指定尺寸的缩略图？

提前致谢！

Answer 1

public static Bitmap transform(Matrix scaler, Bitmap source, int targetWidth, int targetHeight, boolean scaleUp) {
    int deltaX = source.getWidth() - targetWidth;
    int deltaY = source.getHeight() - targetHeight;
    if (!scaleUp && (deltaX < 0 || deltaY < 0)) {
        /*
         * In this case the bitmap is smaller, at least in one dimension,
         * than the target. Transform it by placing as much of the image as
         * possible into the target and leaving the top/bottom or left/right
         * (or both) black.
         */
        Bitmap b2 = Bitmap.createBitmap(targetWidth, targetHeight, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(b2);

        int deltaXHalf = Math.max(0, deltaX / 2);
        int deltaYHalf = Math.max(0, deltaY / 2);
        Rect src = new Rect(deltaXHalf, deltaYHalf, deltaXHalf + Math.min(targetWidth, source.getWidth()), deltaYHalf
                + Math.min(targetHeight, source.getHeight()));
        int dstX = (targetWidth - src.width()) / 2;
        int dstY = (targetHeight - src.height()) / 2;
        Rect dst = new Rect(dstX, dstY, targetWidth - dstX, targetHeight - dstY);
        c.drawBitmap(source, src, dst, null);
        return b2;
    }
    float bitmapWidthF = source.getWidth();
    float bitmapHeightF = source.getHeight();

    float bitmapAspect = bitmapWidthF / bitmapHeightF;
    float viewAspect = (float) targetWidth / targetHeight;

    if (bitmapAspect > viewAspect) {
        float scale = targetHeight / bitmapHeightF;
        if (scale < .9F || scale > 1F) {
            scaler.setScale(scale, scale);
        } else {
            scaler = null;
        }
    } else {
        float scale = targetWidth / bitmapWidthF;
        if (scale < .9F || scale > 1F) {
            scaler.setScale(scale, scale);
        } else {
            scaler = null;
        }
    }

    Bitmap b1;
    if (scaler != null) {
        // this is used for minithumb and crop, so we want to filter here.
        b1 = Bitmap.createBitmap(source, 0, 0, source.getWidth(), source.getHeight(), scaler, true);
    } else {
        b1 = source;
    }

    int dx1 = Math.max(0, b1.getWidth() - targetWidth);
    int dy1 = Math.max(0, b1.getHeight() - targetHeight);

    Bitmap b2 = Bitmap.createBitmap(b1, dx1 / 2, dy1 / 2, targetWidth, targetHeight);

    if (b1 != source) {
        b1.recycle();
    }

    return b2;
}