login image converted from JPG to PNG

[gigaforall]

Steps to reproduce

1.submit a new login image in the Theming section
2.Check image size and type on login page

Expected behaviour

Image should stay jpg

Actual behaviour

image is converted to PNG and size is getting enormous

Server configuration

Operating system:
Ubuntu 20.04
Web server:
Apache2
Database:
MariaDB 10.05
PHP version:
7.4.3
Nextcloud version: (see Nextcloud admin page)
20.03
Updated from an older Nextcloud/ownCloud or fresh install:
fresh
Where did you install Nextcloud from:
nextcloud.com
Signing status:

Signing status

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

App list

- accessibility: 1.6.0 - activity: 2.13.4 - admin_audit: 1.10.0 - bruteforcesettings: 2.0.1 - calendar: 2.1.2 - cloud_federation_api: 1.3.0 - comments: 1.10.0 - contacts: 3.4.2 - contactsinteraction: 1.1.0 - dav: 1.16.1 - event_update_notification: 1.1.0 - federatedfilesharing: 1.10.1 - files: 1.15.0 - files_pdfviewer: 2.0.1 - files_rightclick: 0.17.0 - files_sharing: 1.12.0 - files_trashbin: 1.10.1 - files_versions: 1.13.0 - files_videoplayer: 1.9.0 - logreader: 2.5.0 - lookup_server_connector: 1.8.0 - mail: 1.7.2 - notes: 4.0.1 - notifications: 2.8.0 - oauth2: 1.8.0 - password_policy: 1.10.1 - photos: 1.2.1 - provisioning_api: 1.10.0 - recommendations: 0.8.0 - richdocuments: 3.7.11 - serverinfo: 1.10.0 - settings: 1.2.0 - sharebymail: 1.10.0 - systemtags: 1.10.0 - tasks: 0.13.6 - text: 3.1.0 - theming: 1.11.0 - theming_customcss: 1.7.0 - twofactor_backupcodes: 1.9.0 - user_status: 1.0.1 - viewer: 1.4.0 - weather_status: 1.0.0 - workflowengine: 2.2.0 Disabled: - dashboard - encryption - federation - files_external - firstrunwizard - nextcloud_announcements - privacy - spreed - support - survey_client - updatenotification - user_ldap

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

Nextcloud configuration:

Config report

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or 

Insert your config.php content here. 
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)
```{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "domain.com"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "simpleSignUpLink.shown": false,
        "htaccess.RewriteBase": "\/",
        "knowledgebaseenabled": false,
        "skeletondirectory": "\/home\/nextclouddefaults",
        "dbtype": "mysql",
        "version": "20.0.3.2",
        "overwrite.cli.url": "https:\/\/domain.com",
        "enable_previews": false,
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "memcache.local": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "filelocking.enabled": "true",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0,
            "timeout": 0
        },
        "maintenance": false,
        "loglevel": 2,
        "mail_smtpmode": "smtp",
        "mail_smtpsecure": "ssl",
        "mail_sendmailmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpauth": 1,
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465"
    }
}

</details>

**Are you using external storage, if yes which one:** local/smb/sftp/...
smb
**Are you using encryption:** yes/no
no
**Are you using an external user-backend, if yes which one:** LDAP/ActiveDirectory/Webdav/...
no
#### LDAP configuration (delete this part if not used)
<details>
<summary>LDAP config</summary>

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your Nextcloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM oc_appconfig WHERE appid = 'user_ldap';

Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

</details>

### Client configuration
**Browser:**

**Operating system:**

### Logs

<!--- Reports without logs might be closed as unqualified reports! -->

#### Web server error log
<details>
<summary>Web server error log</summary>

Insert your webserver log here

</details>

#### Nextcloud log (data/nextcloud.log)
<details>
<summary>Nextcloud log</summary>

Insert your Nextcloud log here

</details>

#### Browser log
<details>
<summary>Browser log</summary>

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

</details>

[landryb]

Stumbled upon this issue; uploading a 1Mb jpeg file converts it to a 18Mb PNG24 file, afaict because the code inconditionally converts the uploaded file to png24 in https://github.com/nextcloud/server/blob/master/apps/theming/lib/ImageManager.php#L227

an ugly workaround is to put your JPEG background file directly in the nextcloud data directory, replacing the generated PNG24 file in appdata_<instanceid>/theming/images/background. It works here on 21 but that's a bit gross.

[Freeedim]

Hi there!

I don't know exactly what progress has been made on this. I see the issue is still open, while when I upload a jpg background image, it stays a jpg image.

However, on my NC 22.x.x (up to 22.2.6 at least) my original jpg image is less than 1 MB (1920x1080), and the displayed one is 3 MB (same resolution). Shall I open a new issue, or will this be solved with this one?

[aosmirnov]

Issue is still presented in 23.0.3. I've uploaded a 354KB JPG image and got 3318KB PNG in login page background. It has the same resolution as original (1980x1024) but has 10 times bigger size. Managed to fix this using Custom CSS app.

[gigaforall]

The issue is still there, on every version till now on 25.0.3 , I tried to re upload a new image to check if it was resolved, but that is sadly not the case.
will submit a new bug report on the link you sent as soon as I can, thank you for looking into it.

[Freeedim]

Same here, issue still relevant.

[joshtrichards]

Duplicate of #34233
Fixed in #36471