From 0bb8cb9203e134e77cd0e4dc0bb091da6ff63541 Mon Sep 17 00:00:00 2001
From: Randy Ridge <randyridge@gmail.com>
Date: Tue, 29 Dec 2020 09:29:51 -0500
Subject: [PATCH] Ensure TIFF is cast when using float predictor (#2502)

---
 docs/changelog.md | 4 ++++
 src/pipeline.cc   | 4 ++++
 test/unit/tiff.js | 4 ++--
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index 4122804b..378a6612 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -6,6 +6,10 @@ Requires libvips v8.10.5
 
 ### v0.27.1 - TBD
 
+* Ensure TIFF is cast when using float predictor.
+  [#2502](https://github.com/lovell/sharp/pull/2502)
+  [@randyridge](https://github.com/randyridge)
+
 * Add support for Uint8Array and Uint8ClampedArray input.
   [#2511](https://github.com/lovell/sharp/pull/2511)
   [@leon](https://github.com/leon)
diff --git a/src/pipeline.cc b/src/pipeline.cc
index 70609396..da4b87f6 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -955,6 +955,10 @@ class PipelineWorker : public Napi::AsyncWorker {
             sharp::AssertImageTypeDimensions(image, sharp::ImageType::JPEG);
             baton->channels = std::min(baton->channels, 3);
           }
+          // Cast pixel values to float, if required
+          if (baton->tiffPredictor == VIPS_FOREIGN_TIFF_PREDICTOR_FLOAT) {
+            image = image.cast(VIPS_FORMAT_FLOAT);
+          }
           image.tiffsave(const_cast<char*>(baton->fileOut.data()), VImage::option()
             ->set("strip", !baton->withMetadata)
             ->set("Q", baton->tiffQuality)
diff --git a/test/unit/tiff.js b/test/unit/tiff.js
index 3facb275..7bd21330 100644
--- a/test/unit/tiff.js
+++ b/test/unit/tiff.js
@@ -277,7 +277,7 @@ describe('TIFF', function () {
       });
   });
 
-  it('TIFF deflate compression with float predictor shrinks test file', function (done) {
+  it('TIFF deflate compression of integral input with float predictor increases file size', function (done) {
     const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
     sharp(fixtures.inputTiffUncompressed)
       .tiff({
@@ -287,7 +287,7 @@ describe('TIFF', function () {
       .toFile(fixtures.outputTiff, (err, info) => {
         if (err) throw err;
         assert.strictEqual('tiff', info.format);
-        assert(info.size < startSize);
+        assert(info.size > startSize);
         rimraf(fixtures.outputTiff, done);
       });
   });