From 1e4597c284f3d572f4cd21d5bbb3fc0523f77ce9 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Sun, 10 Mar 2019 17:26:26 +0000
Subject: [PATCH] Changelog entry for #1595 (plus add GIF)

---
 docs/changelog.md |  4 ++++
 lib/input.js      |  2 +-
 src/common.cc     | 14 ++++++++++++--
 src/common.h      |  5 +++++
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index cc372ca2..676f0bb4 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -12,6 +12,10 @@ Requires libvips v8.7.4.
 * Add `composite` operation supporting multiple images and blend modes; deprecate `overlayWith`.
   [#728](https://github.com/lovell/sharp/issues/728)
 
+* Add support for `page` input option to GIF and PDF.
+  [#1595](https://github.com/lovell/sharp/pull/1595)
+  [@ramiel](https://github.com/ramiel)
+
 ### v0.21 - "*teeth*"
 
 Requires libvips v8.7.0.
diff --git a/lib/input.js b/lib/input.js
index 10155e0f..3779c0f5 100644
--- a/lib/input.js
+++ b/lib/input.js
@@ -57,7 +57,7 @@ function _createInputDescriptor (input, inputOptions, containerOptions) {
         throw new Error('Expected width, height and channels for raw pixel input');
       }
     }
-    // Page input for multi-page TIFF
+    // Page input for multi-page images (GIF, TIFF, PDF)
     if (is.defined(inputOptions.page)) {
       if (is.integer(inputOptions.page) && is.inRange(inputOptions.page, 0, 100000)) {
         inputDescriptor.page = inputOptions.page;
diff --git a/src/common.cc b/src/common.cc
index 6d3f870c..6e9b091e 100644
--- a/src/common.cc
+++ b/src/common.cc
@@ -212,6 +212,16 @@ namespace sharp {
     return imageType;
   }
 
+  /*
+    Does this image type support multiple pages?
+  */
+  bool ImageTypeSupportsPage(ImageType imageType) {
+    return
+      imageType == ImageType::GIF ||
+      imageType == ImageType::TIFF ||
+      imageType == ImageType::PDF;
+  }
+
   /*
     Open an image from the given InputDescriptor (filesystem, compressed buffer, raw pixel data)
   */
@@ -243,7 +253,7 @@ namespace sharp {
             if (imageType == ImageType::MAGICK) {
               option->set("density", std::to_string(descriptor->density).data());
             }
-            if (imageType == ImageType::TIFF || imageType == ImageType::PDF) {
+            if (ImageTypeSupportsPage(imageType)) {
              option->set("page", descriptor->page);
             }
             image = VImage::new_from_buffer(descriptor->buffer, descriptor->bufferLength, nullptr, option);
@@ -288,7 +298,7 @@ namespace sharp {
             if (imageType == ImageType::MAGICK) {
               option->set("density", std::to_string(descriptor->density).data());
             }
-            if (imageType == ImageType::TIFF || imageType == ImageType::PDF) {
+            if (ImageTypeSupportsPage(imageType)) {
              option->set("page", descriptor->page);
             }
             image = VImage::new_from_file(descriptor->file.data(), option);
diff --git a/src/common.h b/src/common.h
index 210558d3..4da7f361 100644
--- a/src/common.h
+++ b/src/common.h
@@ -140,6 +140,11 @@ namespace sharp {
   */
   ImageType DetermineImageType(char const *file);
 
+  /*
+    Does this image type support multiple pages?
+  */
+  bool ImageTypeSupportsPage(ImageType imageType);
+
   /*
     Open an image from the given InputDescriptor (filesystem, compressed buffer, raw pixel data)
   */