[emacs] belf: extract first page of pdf as cover

1 files changed, 29 insertions, 13 deletions

diff --git a/emacs/.emacs.d/lisp/my/belf.el b/emacs/.emacs.d/lisp/my/belf.el
index 0e7a557..9eef0b8 100644
--- a/emacs/.emacs.d/lisp/my/belf.el
+++ b/emacs/.emacs.d/lisp/my/belf.el
@@ -162,24 +162,40 @@
             found (file-exists-p cover-file-name)))
     (when found cover-file-name)))
 
+(defun belf-pdf-page-one-cover (file-name)
+  "Extract the first page of a pdf file as cover."
+  (let ((cover-file (file-name-with-extension file-name "jpg")))
+    (with-temp-buffer
+      (if (eq 0
+              (call-process "gs" nil t t
+                            "-dNOPAUSE" "-dBATCH" "-sDEVICE=jpeg" "-r300"
+                            (format "-sOutputFile=%s" cover-file)
+                            "-dFirstPage=1" "-dLastPage=1" file-name))
+          cover-file
+        (message "Failed to extract cover from PDF: %s" (buffer-string))
+        nil))))
+
 (defun belf-book-cover (file-name)
   "Get book cover.
 
 First look for an image file with the same file name.
 Then for PDF, extract the first page.
-For EPUB, looks for a cover image in the file. If not found, extract the first page."
-  (when-let ((cover-file-name (belf-locate-book-cover file-name)))
-    (concat "file://" cover-file-name))
-  (when (equal "epub" (file-name-extension file-name))
-    (when-let* ((content-file-name (belf-epub-content-file-name file-name))
-                (cover-file
-                 (belf-epub-cover-file-name file-name content-file-name))
-                (cover-file-name (file-name-with-extension
-                                  file-name
-                                  (file-name-extension cover-file))))
-      (call-process "unzip" nil `(:file ,cover-file-name) nil
-                    "-p" file-name cover-file)
-      (concat "file://" cover-file-name)))
+For EPUB, looks for a cover image in the file."
+  (if-let ((cover-file-name (belf-locate-book-cover file-name)))
+      (concat "file://" cover-file-name)
+    (when (equal "epub" (file-name-extension file-name))
+      (when-let* ((content-file-name (belf-epub-content-file-name file-name))
+                  (cover-file
+                   (belf-epub-cover-file-name file-name content-file-name))
+                  (cover-file-name (file-name-with-extension
+                                    file-name
+                                    (file-name-extension cover-file))))
+        (call-process "unzip" nil `(:file ,cover-file-name) nil
+                      "-p" file-name cover-file)
+        (format "file://%s" cover-file-name)))
+    (when (equal "pdf" (file-name-extension file-name))
+      (when (setq cover-file-name (belf-pdf-page-one-cover file-name))
+        (format "file://%s" cover-file-name))))
   )
 
 (defun belf-book-infobox-at-point ()