Add support for TIFF float predictor

src/pipeline.cc

@@ -838,6 +838,10 @@ class PipelineWorker : public Nan::AsyncWorker {
             ->set("alpha_q", baton->webpAlphaQuality));
           baton->formatOut = "webp";
         } else if (baton->formatOut == "tiff" || isTiff || (matchInput && inputImageType == ImageType::TIFF)) {
+          // Cast pixel values to float, if required
+          if (baton->tiffPredictor == VIPS_FOREIGN_TIFF_PREDICTOR_FLOAT) {
+            image = image.cast(VIPS_FORMAT_FLOAT);
+          }
           // Write TIFF to file
           image.tiffsave(const_cast<char*>(baton->fileOut.data()), VImage::option()
             ->set("strip", !baton->withMetadata)

test/unit/io.js

@@ -864,71 +864,75 @@ describe('Input/output', function () {
   it('TIFF lzw compression with horizontal predictor shrinks test file', function (done) {
     const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
     sharp(fixtures.inputTiffUncompressed)
-          .tiff({
+      .tiff({
-            compression: 'lzw',
+        compression: 'lzw',
-            force: true,
+        predictor: 'horizontal'
-            // note: lzw compression is imperfect and sometimes
+      })
-            // generates larger files, as it does with this input
+      .toFile(fixtures.outputTiff, (err, info) => {
-            // if no predictor is used.
+        if (err) throw err;
-            predictor: 'horizontal'
+        assert.strictEqual('tiff', info.format);
-          })
+        assert(info.size < startSize);
-          .toFile(fixtures.outputTiff, (err, info) => {
+        fs.unlink(fixtures.outputTiff, done);
-            if (err) throw err;
+      });
-            assert.strictEqual('tiff', info.format);
-            assert(info.size < startSize);
-            fs.unlinkSync(fixtures.outputTiff);
-            done();
-          });
   });
 
   it('TIFF deflate compression with hoizontal predictor shrinks test file', function (done) {
     const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
     sharp(fixtures.inputTiffUncompressed)
-          .tiff({
+      .tiff({
-            compression: 'deflate',
+        compression: 'deflate',
-            force: true,
+        predictor: 'horizontal'
-            predictor: 'horizontal'
+      })
-          })
+      .toFile(fixtures.outputTiff, (err, info) => {
-          .toFile(fixtures.outputTiff, (err, info) => {
+        if (err) throw err;
-            if (err) throw err;
+        assert.strictEqual('tiff', info.format);
-            assert.strictEqual('tiff', info.format);
+        assert(info.size < startSize);
-            assert(info.size < startSize);
+        fs.unlink(fixtures.outputTiff, done);
-            fs.unlinkSync(fixtures.outputTiff);
+      });
-            done();
+  });
-          });
+
+  it('TIFF deflate compression with float predictor shrinks test file', function (done) {
+    const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
+    sharp(fixtures.inputTiffUncompressed)
+      .tiff({
+        compression: 'deflate',
+        predictor: 'float'
+      })
+      .toFile(fixtures.outputTiff, (err, info) => {
+        if (err) throw err;
+        assert.strictEqual('tiff', info.format);
+        assert(info.size < startSize);
+        fs.unlink(fixtures.outputTiff, done);
+      });
   });
 
   it('TIFF deflate compression without predictor shrinks test file', function (done) {
     const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
     sharp(fixtures.inputTiffUncompressed)
-          .tiff({
+      .tiff({
-            compression: 'deflate',
+        compression: 'deflate',
-            force: true,
+        predictor: 'none'
-            predictor: 'none'
+      })
-          })
+      .toFile(fixtures.outputTiff, (err, info) => {
-          .toFile(fixtures.outputTiff, (err, info) => {
+        if (err) throw err;
-            if (err) throw err;
+        assert.strictEqual('tiff', info.format);
-            assert.strictEqual('tiff', info.format);
+        assert(info.size < startSize);
-            assert(info.size < startSize);
+        fs.unlink(fixtures.outputTiff, done);
-            fs.unlinkSync(fixtures.outputTiff);
+      });
-            done();
-          });
   });
 
   it('TIFF jpeg compression shrinks test file', function (done) {
     const startSize = fs.statSync(fixtures.inputTiffUncompressed).size;
     sharp(fixtures.inputTiffUncompressed)
-          .tiff({
+      .tiff({
-            compression: 'jpeg',
+        compression: 'jpeg'
-            force: true
+      })
-          })
+      .toFile(fixtures.outputTiff, (err, info) => {
-          .toFile(fixtures.outputTiff, (err, info) => {
+        if (err) throw err;
-            if (err) throw err;
+        assert.strictEqual('tiff', info.format);
-            assert.strictEqual('tiff', info.format);
+        assert(info.size < startSize);
-            assert(info.size < startSize);
+        fs.unlink(fixtures.outputTiff, done);
-            fs.unlinkSync(fixtures.outputTiff);
+      });
-            done();
-          });
   });
 
   it('TIFF none compression does not throw error', function () {