Image not filling the whole A4 paper

Hello i am using LibreOffice to convert png to pdf , my problem now is that whenever i open a png with LibeOffice it does not fill the whole page , there is always a white border like you see in the attachement , even tho the image is made to fit in a whole A4 page, i can manually resize the image to fit everything , but i want this to happen by default

LibreOffice v 7.5
Windows 10

Page>Page Properties will allow you to change page margins.

Unfortunately, there is no page style in Draw to keep your new settings.

The work around is to save a blank document with all your custom settings (not only page configuration) into a Draw template with File>Templates>Save as Template and …>Manage Template to make it known by Draw (and optionally make it your own default template).

PS: when asking here, always mantion OS name and LO version so that answers may take into consideration the subtle differences between platforms and releases.

Hello thank you for replying , on the right side theres page properties tab i set the margins to none , that semi fixed it , theres still a slight margin on top and bottom of the page , but now the problem , i set the default template to that with no margins , but whenever i open an image it does not open with the default template that i set , it opens with the default of LibreOffice.
i want to achieve whenever i open an image with LibreOffice it just fills the whole page without me doing anything , because i will be running the convert to pdf command from the command-line
and it is currently converting it with the white margins

How did you turn your template into default?
The default template is used when creating a blank document. It is possible that the default template is not invoked when you force-open an existing document, be it a PNG file, as the document is supposed to be already associated with a template (even considering a PNG file is not a Draw document). So, maybe you should manually import the image into a new Draw document. It is not clear in your question if you want to convert headless (using a command line in a terminal). This would probably require first a manual step to force the correct template.

when i created the template there was a “set as default” checkmark ,
but yeah its not using it when opening the image directly
i was hoping i can just convert a png to a pdf without anything changing , like these online tools do it
i chose LibreOffice because it has a command line i can use without opening the app and is free
i will look more into it , thank you for helping