Android图片操作-生成缩略图

// 可用于生成缩略图。
    /**
     * Creates a centered bitmap of the desired size. Recycles the input.
     * 
     * @param source
     */
    public static Bitmap extractMiniThumb(Bitmap source, int width, int height) {
        return extractMiniThumb(source, width, height, true);
    }

    public static Bitmap extractMiniThumb(Bitmap source, int width, int height,
            boolean recycle) {
        if (source == null) {
            return null;
        }

        float scale;
        if (source.getWidth() < source.getHeight()) {
            scale = width / (float) source.getWidth();
        } else {
            scale = height / (float) source.getHeight();
        }
        Matrix matrix = new Matrix();
        matrix.setScale(scale, scale);
        Bitmap miniThumbnail = transform(matrix, source, width, height, false);

        if (recycle && miniThumbnail != source) {
            source.recycle();
        }
        return miniThumbnail;
    }

    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;
    }

 

转载于:https://www.cnblogs.com/liuhongzhe-5240/archive/2012/08/08/2628284.html