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<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="MagentoThemeModelViewDesign">
        <arguments>
            <argument name="themes" xsi:type="array">
                <item name="adminhtml" xsi:type="string">Adminlogo/Changelogo</item>
            </argument>
        </arguments>
    </type>
</config>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
     <module name="Adminlogo_Changelogo" setup_version="1.0.0">
         <sequence>
             <module name="Magento_Theme"/>
         </sequence>
     </module>
 </config>

<?php
    MagentoFrameworkComponentComponentRegistrar::register(
        MagentoFrameworkComponentComponentRegistrar::MODULE,
        'Adminlogo_Changelogo',
        __DIR__
    );
    ?>

<?php
    MagentoFrameworkComponentComponentRegistrar::register(
        MagentoFrameworkComponentComponentRegistrar::THEME,
        'adminhtml/mythme/logotheme',
        __DIR__
    );


    ?>

<theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
        <title>astrokapoor astrology</title>
        <parent>Magento/backend</parent>
    </theme>

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="admin-login" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
            <update handle="styles" />
            <body>
                <referenceBlock name="logo">
                    <arguments>
                        <argument name="logo_image_src" xsi:type="string">images/my_logo.png</argument>
                    </arguments>
                </referenceBlock>
            </body>
        </page>

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
        <body>
            <referenceContainer name="header">
                <referenceBlock name="logo">
                    <arguments>
                        <argument name="logo_img_width" xsi:type="number">300</argument>
                        <argument name="logo_img_height" xsi:type="number">300</argument>
                        <argument name="show_part" xsi:type="string">logo</argument>
                        <argument name="edition" translate="true" xsi:type="string">Community Edition</argument>
                        <argument name="logo_image_src" xsi:type="string">images/astrokapoor_logo.png</argument>
                    </arguments>
                </referenceBlock>
            </referenceContainer>
        </body>
    </page>