I'm trying to install a *.png file as a custom header using the Twenty Thirteen theme. The file contains a client's logo, site name, and tag line, and is 750 px wide x 175 px high.
When I attempt to install the file in the header, the theme automatically tries to crop the file's height and width. The cropped file fails to show all the formatting I generated with my graphics editor. Using the parent theme, when I crop the custom header to the maximum permitted size and save my changes, the theme expands the file width beyond the view of my computer monitor (I presume out to 1600 px wide, the header default width for Twenty Thirteen). The text and images in the custom header look pixelated and ragged, and both ends of the logo are cut off. This is not acceptable.
The solution seem to lie in creating a child theme, with modifications to the parent style.css and functions. php files within the child theme folder.
I modified the allowable height of a custom header to 400 px as described in the following thread. The child theme fully accepted the height of the logo (175 px H), while cropping less of the width than the parent theme. When I viewed the home page of the site, both ends of the logo were chopped off, and the logo continue to look ragged, although less so than just using the parent theme. Worse, the CSS of the navigation bar failed to install.
I'm at a complete loss as to how to fix this issue. I suspect that the topic thread referenced above is not the complete solution. The parent theme custom-header.php file has default settings for header height and width. Should I modify those values in my child theme as well?