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FoxyLoxy's avatar
FoxyLoxy
New member | Level 2
4 years ago

Acces thumbnail images for PDFs

I'm using Dropbox to store PDF files, and my external application needs to programmatically access a thumbnail image of the first page for each of these PDF files.   These thumbnail images need t...
API
Greg-DB's avatar
Greg-DB
Icon for Dropbox Community Moderator rankDropbox Community Moderator
4 years ago

FoxyLoxy That's correct, /2/files/get_thumbnail_v2 technically can return thumbnails for PDF files. It doesn't officially document support for PDF files in particular though, so I can't officially recommend relying on that. I will send this along as a request to consider that officially supported, but I can't promise if or when that might be done.

 

Здравко You mentioned you're getting an "Internal Server Error" on some piece of functionality. Can you share the details so we can look into it? Thanks in advance!

Здравко's avatar
Здравко
Legendary | Level 20
4 years ago
Greg-DB wrote:

...

ЗдравкоYou mentioned you're getting an "Internal Server Error" on some piece of functionality. Can you share the details so we can look into it? Thanks in advance!

Hi Greg-DB,

Sure, I can. In 2/files/get_thumbnail_v2 description can be seen that connection to this end point can be authenticated using App Authentication. Such type of authentication assumes possibility of using both POST and GET request. Also, authentication and argument should be able pass either as header or as parameters and both are assumed equivalent. Yes but no!!! When I pass headers using GET request:

curl -s -S -o ~/dump.jpg -D - -u "<app key>:<app secret>" -H "Dropbox-API-Arg: {\"resource\": {\".tag\": \"link\",\"url\": \"<shared link>\"},\"size\": \"w64h64\"}" https://content.dropboxapi.com/2/files/get_thumbnail_v2

The result is as expected. Here <app key> and <app secret> are valid ones. <shared link> is valid link to a file able to produce thumbnail. In my case I use a link to arbitrary PDF in my account.

When I try pass the same (or equivalent thing, according to documentation) as parameters:

curl -s -S -o ~/dump.txt -D - -g "https://content.dropboxapi.com/2/files/get_thumbnail_v2?arg={\"resource\":{\".tag\":\"link\",\"url\":\"<shared link>\"},\"size\":\"w128h128\"}&authorization=Basic%20<base64 key&secret>"

 Where <shared link> is the same as above and <base64 key&secret> is produced according documentation from <app key> and <app secret>. Follows the result (response body is empty):

HTTP/1.1 500 Internal Server Error
Server: envoy
Date: Wed, 23 Feb 2022 19:17:38 GMT
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Cache-Control: no-cache
Vary: Dropbox-API-Arg, Authorization, Accept-Encoding
Content-Disposition: attachment; filename=unspecified
Content-Security-Policy: sandbox
X-Webkit-Csp: sandbox
X-Content-Security-Policy: sandbox
Content-Security-Policy: sandbox allow-forms allow-scripts
X-Robots-Tag: noindex, nofollow, noimageindex
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Robots-Tag: noindex, nofollow, noimageindex
X-Dropbox-Response-Origin: remote
X-Dropbox-Request-Id: 81e8c25c686642a3b479972366796ab9
Transfer-Encoding: chunked

I have no idea what's wrong here! As a consequence, such request can not be encoded in a simple link. The same is the result when I try to in web browser (I checked in Firefox). That's it.

  • Greg-DB's avatar
    Greg-DB
    Icon for Dropbox Community Moderator rankDropbox Community Moderator
    4 years ago

    Здравко Thanks! That's helpful. I just checked on this, and it looks like that failure is due to an invalid app key and/or secret value, so please double check your values. Additionally, there seems to be a bug on our side with how we handle that error case, resulting in the 500 Internal Server Error being returned, instead of a useful error message/response. I'll ask the team to fix that up.

    • Здравко's avatar
      Здравко
      Legendary | Level 20
      4 years ago
      Greg-DB wrote:

      ... it looks like that failure is due to an invalid app key and/or secret value, so please double check your values. ...

      Ok, Might be, but there is no reliable way I check it. The following is the way I use to get authentication values. I repeated the test with the same result.

      curl -s -S -o ~/dump.txt -D - -g "https://content.dropboxapi.com/2/files/get_thumbnail_v2?arg={\"resource\":{\".tag\":\"link\",\"url\":\"<shared link>\"},\"size\":\"w128h128\"}&authorization=Basic%20$(echo "<app key>:<app secret>" | base64)"

      Here used values are correct for sure; they are same as above (first command), but fails still (second command). Is the used algorithm wrong? 🤔 I thought it's the same as described, but...

      • Greg-DB's avatar
        Greg-DB
        Icon for Dropbox Community Moderator rankDropbox Community Moderator
        4 years ago

        Здравко You need to use "echo -n " instead of just "echo" in this case. When you don't set "-n", echo includes a trailing newline character which will corrupt your encoded app key/secret value.

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