Progressive JPEG

DEVELOPMENT.md

@@ -143,11 +143,12 @@ a raw pixels buffer and encode it into a jpeg image buffer.
 The arguments for the encoding methods differ for each encoding format.
 We list them here:
 
-0. JPEG: `encoder.jpeg(pixbuff, width, height, quality, callback)`
+0. JPEG: `encoder.jpeg(pixbuff, width, height, quality, progressive, callback)`
     0. `pixbuff` - Raw RGBA pixels buffer (a Buffer object)
     0. `width` - The with of the image
     0. `height` - The height of the image
     0. `quality` - JPEG quality (0-100)
+    0. `progressive` - should produce progressive JPEG (true/false)
     0. `callback` - callback function
 0. PNG: `encoder.png(pixbuff, width, height, compression, interlaced, trans, callback)`
     0. `pixbuff` - Raw RGBA pixels buffer (a Buffer object)

README.md

@@ -651,6 +651,7 @@ encoded data as a NodeJS Buffer object.
 The `params` object should have the following fields:
 
 - `quality {Integer}`: Defaults to `100`.
+- `progressive {Boolean}`: Defaults to `false`.
 
 Note that when encoding to JPEG the alpha channel is discarded.
 

examples/progressive.js

@@ -0,0 +1,15 @@
+/**
+ * Example for using LWIP to shift image's hue by 50 degrees.
+ */
+
+var path = require('path'),
+    lwip = require('../');
+
+lwip.open('lena.jpg', function(err, image) {
+    if (err) return console.log(err);
+    image.writeFile('lena_progressive.jpg', 'jpg', { progressive: true },
+        function(err) {
+            if (err) return console.log(err);
+            console.log('done');
+        });
+});

lib/ImagePrototypeInit.js

@@ -560,6 +560,7 @@
                             that.__lwip.width(),
                             that.__lwip.height(),
                             params.quality,
+                            params.progressive,
                             encoderCb
                         );
                     } else if (type === 'png') {

lib/util.js

@@ -115,6 +115,9 @@
         if (params.quality != parseInt(params.quality) ||
             params.quality < 0 || params.quality > 100)
             throw Error('Invalid JPEG quality');
+        if (params.progressive) params.progressive = true;
+        else params.progressive = false;
+
     }
 
     function getClosest2Exp(num){

src/encoder/encoder.h

@@ -30,6 +30,7 @@ class EncodeToJpegBufferWorker : public Nan::AsyncWorker {
         size_t width,
         size_t height,
         int quality,
+        bool progressive,
         Nan::Callback * callback
     );
     ~EncodeToJpegBufferWorker();
@@ -42,6 +43,7 @@ class EncodeToJpegBufferWorker : public Nan::AsyncWorker {
     int _quality;
     char * _jpegbuf;
     size_t _jpegbufsize;
+    bool _progressive;
 };
 
 class EncodeToPngBufferWorker : public Nan::AsyncWorker {

src/encoder/init.cpp

@@ -1,21 +1,23 @@
 #include "encoder.h"
 
-// encoder.jpeg(pixbuf, width, height, quality, callback)
+// encoder.jpeg(pixbuf, width, height, quality, progressive, callback)
 NAN_METHOD(encodeToJpegBuffer) {
     Nan::HandleScope();
 
     Local<Object> buff = info[0].As<Object>();
     size_t width = info[1].As<Integer>()->Value();
     size_t height = info[2].As<Integer>()->Value();
     int quality = info[3].As<Integer>()->Value();
-    Nan::Callback * callback = new Nan::Callback(info[4].As<Function>());
+    bool progressive = info[4].As<Boolean>()->Value();
+    Nan::Callback * callback = new Nan::Callback(info[5].As<Function>());
 
     Nan::AsyncQueueWorker(
         new EncodeToJpegBufferWorker(
             buff,
             width,
             height,
             quality,
+            progressive,
             callback
         ));
 }

src/encoder/jpeg_worker.cpp

@@ -7,9 +7,10 @@ EncodeToJpegBufferWorker::EncodeToJpegBufferWorker(
     size_t width,
     size_t height,
     int quality,
+    bool progressive,
     Nan::Callback * callback
 ): Nan::AsyncWorker(callback), _width(width), _height(height),
-    _quality(quality), _jpegbuf(NULL), _jpegbufsize(0) {
+    _quality(quality), _jpegbuf(NULL), _jpegbufsize(0), _progressive(progressive) {
     SaveToPersistent("buff", buff); // make sure buff isn't GC'ed
     _pixbuf = (unsigned char *) Buffer::Data(buff);
 }
@@ -45,8 +46,12 @@ void EncodeToJpegBufferWorker::Execute () {
     cinfo.image_height = _height;
     cinfo.input_components = dimbuf;
     cinfo.in_color_space = colortype;
+    cinfo.progressive_mode = (boolean)_progressive;
     jpeg_set_defaults(&cinfo);
     jpeg_set_quality(&cinfo, _quality, TRUE);
+    if (_progressive) {
+        jpeg_simple_progression(&cinfo);
+    }
     jpeg_start_compress(&cinfo, TRUE);
 
     // shared memory cimg. no new memory is allocated.

tests/02.operations/101.writeFile.js

@@ -52,6 +52,14 @@ describe('lwip.writeFile', function() {
                 });
             });
 
+            describe('params specified progressive=true', function() {
+                if('should succeed', function(done) {
+                    image.writeFile(outpathJpeg, {
+                        progressive: true
+                    }, done);
+                });
+            });
+
         });
 
         describe('with type specified', function() {
@@ -65,13 +73,12 @@ describe('lwip.writeFile', function() {
             describe('params specified', function() {
                 it('should succeed', function(done) {
                     image.writeFile(outpathJpeg, 'jpeg', {
-                        quality: 20
+                        quality: 20,
+                        progressive: true,
                     }, done);
                 });
             });
-
         });
-
     });
 
     describe('png', function() {