For SVG, 8192 is the new 256
Prefer librsvg for display of splash.svg When both librsvg and Imagemagick are available, Emacs should prefer librsvg to render SVG images. However, Emacs was using Imagemagick to render its own splash.svg file because image-type-from-file-header returned nil for that file. * lisp/image.el (image-type-from-buffer) (image-type-from-file-header): Look at the first 8192 bytes of the image, not just the first 256. For Emacs’s own splash.svg file, image-type-header-regexps needs to look at 939 bytes. 8192 bytes is a reasonable number nowadays given typical file system design. * test/lisp/image-tests.el (image-tests--emacs-images-directory): New contant. (image-type-from-file-header-test): New test.