Question

我正在将图像上传到服务器，在此之前，我想调整图像尺寸。我用这样的URI得到图像：

Constants.currImageURI = data.getData();

这是上传图片的电话：

String response = uploadUserPhoto(new File(getRealPathFromURI(Constants.currImageURI)));

    public String uploadUserPhoto(File image) {

    DefaultHttpClient mHttpClient;
    HttpParams params = new BasicHttpParams();
    params.setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);
    mHttpClient = new DefaultHttpClient(params);

    try {
        HttpPost httppost = new HttpPost("http://myurl/mobile/image");

        MultipartEntity multipartEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);  
        multipartEntity.addPart("userID", new StringBody(Constants.userID));
        multipartEntity.addPart("uniqueMobileID", new StringBody(Constants.uniqueMobileID));
        multipartEntity.addPart("userfile", new FileBody(image, "mobileimage.jpg", "image/jpeg", "UTF-8"));
        httppost.setEntity(multipartEntity);

        HttpResponse response = mHttpClient.execute(httppost);
        String responseBody = EntityUtils.toString(response.getEntity());

        Log.d(TAG, "response: " + responseBody);
        return responseBody;

    } catch (Exception e) {
       Log.d(TAG, e.getMessage());
    }
    return "";
}

有没有办法根据像素尺寸调整文件大小？

感谢。

Answer 1

使用其他人建议的 Bitmap.createScaledBitmap 。

但是，这个功能不是很聪明。如果你缩小到不到50％的大小，你可能会得到这个：

enter image description here

而不是：

enter image description here

你看到第一张图片的抗锯齿效果不好吗？ createScaledBitmap将为您提供此结果。

原因是像素过滤，如果缩放到＆lt;像素过滤，则会从源中完全跳过某些像素。 50％。

要获得第二个质量结果，如果它比预期结果大2倍，则需要将Bitmap的分辨率减半，然后最后调用createScaledBitmap。

还有更多方法可以将图像减半（或四分之一或变亮）。如果内存中有Bitmap，则递归调用Bitmap.createScaledBitmap将图像减半。

如果从JPG文件加载图像，实现速度更快：使用BitmapFactory.decodeFile并正确设置Options参数，主要是字段inSampleSize，它控制加载图像的子视频，利用JPEG的特性。

许多提供图像缩略图的应用程序盲目使用Bitmap.createScaledBitmap，缩略图只是丑陋。要聪明并使用正确的图像下采样。</ p>

Answer 2

这是来自ThinkAndroid的网址： http://thinkandroid.wordpress.com/2009/12/25/resizing-a-bitmap/

我会研究从资源创建Bitmap或Drawable的可能性，如果你想改变它的大小，请使用下面的代码。

public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
    int width = bm.getWidth();
    int height = bm.getHeight();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;

    // Create a matrix for the manipulation
    Matrix matrix = new Matrix();

    // Resize the bit map
    matrix.postScale(scaleWidth, scaleHeight);

    // Recreate the new Bitmap
    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false);
    return resizedBitmap;

}

编辑：正如其他评论中所建议的那样Bitmap.createScaledBitmap应该在调整大小时用于提高质量。

Answer 3

How to resize a bitmap:

Bitmap.createScaledBitmap(src, dstWidth, dstHeight, filter)

Answer 4

了解Google recommends doing（as @Pointer Null advised）：

public int calculateInSampleSize(
            BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) > reqHeight
                && (halfWidth / inSampleSize) > reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}

我调用上面的内容来调整大图像的大小：

// Check if source and destination exist
// Check if we have read/write permissions

int desired_width = 200;
int desired_height = 200;

BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;

BitmapFactory.decodeFile(SOME_PATH_TO_LARGE_IMAGE, options);

options.inSampleSize = calculateInSampleSize(options, desired_width, desired_height);
options.inJustDecodeBounds = false;

Bitmap smaller_bm = BitmapFactory.decodeFile(src_path, options);

FileOutputStream fOut;
try {
    File small_picture = new File(SOME_PATH_STRING);
    fOut = new FileOutputStream(small_picture);
    // 0 = small/low quality, 100 = large/high quality
    smaller_bm.compress(Bitmap.CompressFormat.JPEG, 50, fOut);
    fOut.flush();
    fOut.close();
    smaller_bm.recycle();
} catch (Exception e) {
    Log.e(LOG_TAG, "Failed to save/resize image due to: " + e.toString());
}

从文件调整图像大小

4 个答案: