Question

如何从完整图像中获取缩略图有几种解决方案，例如
android get thumbnail of image stored on sdcard whose path is known

然而，相反，我需要从缩略图Uri（或缩略图ID）接收完整图像Uri。
以下是我获取缩略图的方法：

fun getGalleryImages(): List<LocalImage> {
    val baseUri: Uri = MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI
    val listOfAllImages = ArrayList<LocalImage>()
    // Set up an array of the Thumbnail Image ID column we want
    val projection = arrayOf(MediaStore.Images.Thumbnails._ID, MediaStore.Images.Thumbnails.IMAGE_ID)
    // Create the cursor pointing to the SDCard
    val cursor = context.contentResolver.query(
            baseUri,
            projection,
            null, 
            null,
            null)

    // Get the column index of the Thumbnails Image ID
    val thumbColumnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID)
    val fullColumnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails.IMAGE_ID)

    var thumbnailUri: Uri?
    while (cursor.moveToNext()) {
        val thumbId = cursor.getString(thumbColumnIndex)
        thumbnailUri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + thumbId)
        // here I save image id for later retrieving full image
        val imageId = cursor.getString(fullColumnIndex)
        listOfAllImages.add(LocalImage(thumbnailUri = thumbnailUri), imId = imageId)
    }
    cursor.close()
    return listOfAllImages
}

然后我必须通过图像ID（或缩略图Uri）检索完整图像

 private fun getFullImage(imageId: String): Uri {
    val projection = arrayOf(MediaStore.Images.Media._ID, MediaStore.Images.Media.DATA)

    val cursor = context.contentResolver.query(
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
            projection,
            MediaStore.Images.Media._ID + "=?",
            arrayOf(imageId),
            null)
    val columnIndex = cursor.getColumnIndex(projection[0])
    if (cursor.moveToFirst()) {
        return Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + cursor.getString(1))
    }
    cursor.close()
    return Uri.EMPTY
}

这给我一个看起来很逼真的Uri：

content://media/external/images/media//storage/emulated/0/DCIM/Camera/IMG_20170720_085045.jpg

但是，Uri似乎无效，因为我无法从中检索图像：

val bitmap = MediaStore.Images.Media.getBitmap(activity.contentResolver, image.imageUri)

java.lang.IllegalStateException：未知URL：content：//media/external/images/media//storage/emulated/0/DCIM/Camera/IMG_20170720_085045.jpg 在android.os.Parcel.readException（Parcel.java:1950）在android.database.DatabaseUtils.readExceptionFromParcel（DatabaseUtils.java:183）在android.database.DatabaseUtils.readExceptionWithFileNotFoundExceptionFromParcel（DatabaseUtils.java:146）在android.content.ContentProviderProxy.openTypedAssetFile（ContentProviderNative.java:698）

Picasso也无法加载此Uri的图像

Answer 1

在获得Uri图像后添加此代码。

if (largeImagePath != null) {

            BitmapFactory.Options opts = new BitmapFactory.Options();
            opts.inSampleSize = OG;
            thumbnail = BitmapFactory.decodeFile((largeImagePath), opts);
            System.gc();
            if (thumbnail != null) {

                try {
                    thumbnail = Common.rotateImageIfRequired(mContext, thumbnail, Uri.fromFile(new File(largeImagePath)));
                } catch (IOException e) {
                    e.printStackTrace();
                }
                imageCam(thumbnail);
            }
        }

public void imageCam(Bitmap thumbnail) {
    Bitmap photo = thumbnail;
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    photo.compress(Bitmap.CompressFormat.JPEG, 100, bos);
    byte b[] = bos.toByteArray();
    encodedImage = Base64.encodeToString(b, Base64.DEFAULT);
    ll_preview.setVisibility(View.VISIBLE);
    img_preview.setVisibility(View.VISIBLE);
    img_preview.setImageBitmap(photo);
}

在Common.java文件中

在其中添加此方法。

  /**
    * Rotate an image if required.
    *
    * @param img           The image bitmap
    * @param selectedImage Image URI
    * @return The resulted Bitmap after manipulation
    */
public static Bitmap rotateImageIfRequired(Context mContext, Bitmap img, Uri selectedImage) throws IOException {

    InputStream input = mContext.getContentResolver().openInputStream(selectedImage);
    ExifInterface ei;
    if (Build.VERSION.SDK_INT > 23)
        ei = new ExifInterface(input);
    else
        ei = new ExifInterface(selectedImage.getPath());

    int orientation = ei.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);

    switch (orientation) {
        case ExifInterface.ORIENTATION_ROTATE_90:
            return rotateImage(img, 90);
        case ExifInterface.ORIENTATION_ROTATE_180:
            return rotateImage(img, 180);
        case ExifInterface.ORIENTATION_ROTATE_270:
            return rotateImage(img, 270);
        default:
            return img;
    }
}

我认为这将解决您的问题

MediaStore.Images从拇指Uri / id

1 个答案: