support reading CMYK, YCCK JPEGs

Fixes Automattic#425

CHANGELOG.md

@@ -87,6 +87,7 @@ canvas.createJPEGStream() // new
  * Provide better, Node.js core-style coded errors for failed sys calls. (For
    example, provide an error with code 'ENOENT' if setting `img.src` to a path
    that does not exist.)
+ * Support reading CMYK, YCCK JPEGs.
 
 ### Added
  * Prebuilds (#992) with different libc versions to the prebuilt binary (#1140)

src/Image.cc

@@ -777,16 +777,30 @@ static void jpeg_mem_src (j_decompress_ptr cinfo, void* buffer, long nbytes) {
 
 #endif
 
+void Image::jpegToARGB(jpeg_decompress_struct* args, uint8_t* data, uint8_t* src, JPEGDecodeL decode) {
+  int stride = naturalWidth * 4;
+  for (int y = 0; y < naturalHeight; ++y) {
+    jpeg_read_scanlines(args, &src, 1);
+    uint32_t *row = (uint32_t*)(data + stride * y);
+    for (int x = 0; x < naturalWidth; ++x) {
+      uint8_t r = 0, g = 0, b = 0;
+      int bx = args->output_components * x;
+      decode(src + bx, r, g, b);
+      uint32_t *pixel = row + x;
+      *pixel = 255 << 24 | r << 16 | g << 8 | b;
+    }
+  }
+}
+
 /*
  * Takes an initialised jpeg_decompress_struct and decodes the
  * data into _surface.
  */
-
+#include <iostream>
 cairo_status_t
 Image::decodeJPEGIntoSurface(jpeg_decompress_struct *args) {
-  int stride = naturalWidth * 4;
   cairo_status_t status;
-
+  
   uint8_t *data = (uint8_t *) malloc(naturalWidth * naturalHeight * 4);
   if (!data) {
     jpeg_abort_decompress(args);
@@ -804,25 +818,30 @@ Image::decodeJPEGIntoSurface(jpeg_decompress_struct *args) {
     return CAIRO_STATUS_NO_MEMORY;
   }
 
-  for (int y = 0; y < naturalHeight; ++y) {
-    jpeg_read_scanlines(args, &src, 1);
-    uint32_t *row = (uint32_t *)(data + stride * y);
-    for (int x = 0; x < naturalWidth; ++x) {
-      if (args->jpeg_color_space == 1) {
-        uint32_t *pixel = row + x;
-        *pixel = 255 << 24
-          | src[x] << 16
-          | src[x] << 8
-          | src[x];
-      } else {
-        int bx = 3 * x;
-        uint32_t *pixel = row + x;
-        *pixel = 255 << 24
-          | src[bx + 0] << 16
-          | src[bx + 1] << 8
-          | src[bx + 2];
-      }
-    }
+  // These are the three main cases to handle. libjpeg converts YCCK to CMYK
+  // and YCbCr to RGB by default.
+  switch (args->out_color_space) {
+    case JCS_CMYK:
+      jpegToARGB(args, data, src, [](uint8_t const* src, uint8_t& r, uint8_t& g, uint8_t& b) {
+        uint16_t k = static_cast<uint16_t>(src[3]);
+        r = k * src[0] / 255;
+        g = k * src[1] / 255;
+        b = k * src[2] / 255;
+      });
+      break;
+    case JCS_RGB:
+      jpegToARGB(args, data, src, [](uint8_t const* src, uint8_t& r, uint8_t& g, uint8_t& b) {
+        r = src[0], g = src[1], b = src[2];
+      });
+      break;
+    case JCS_GRAYSCALE:
+      jpegToARGB(args, data, src, [](uint8_t const* src, uint8_t& r, uint8_t& g, uint8_t& b) {
+        r = g = b = src[0];
+      });
+      break;
+    default:
+      // TODO
+      break;
   }
 
   _surface = cairo_image_surface_create_for_data(

src/Image.h

@@ -10,6 +10,7 @@
 
 #include "Canvas.h"
 #include "CanvasError.h"
+#include <functional>
 
 #ifdef HAVE_JPEG
 #include <jpeglib.h>
@@ -34,7 +35,7 @@
   #endif
 #endif
 
-
+using JPEGDecodeL = std::function<void(uint8_t* const src, uint8_t& r, uint8_t& g, uint8_t& b)>;
 
 class Image: public Nan::ObjectWrap {
   public:
@@ -81,6 +82,7 @@ class Image: public Nan::ObjectWrap {
 #ifdef HAVE_JPEG
     cairo_status_t loadJPEGFromBuffer(uint8_t *buf, unsigned len);
     cairo_status_t loadJPEG(FILE *stream);
+    void jpegToARGB(jpeg_decompress_struct* args, uint8_t* data, uint8_t* src, JPEGDecodeL decode);
     cairo_status_t decodeJPEGIntoSurface(jpeg_decompress_struct *info);
 #if CAIRO_VERSION_MINOR >= 10
     cairo_status_t decodeJPEGBufferIntoMimeSurface(uint8_t *buf, unsigned len);

test/public/tests.js

@@ -1667,6 +1667,27 @@ tests['drawImage(img) jpeg'] = function (ctx, done) {
   img.src = imageSrc('face.jpeg')
 }
 
+tests['drawImage(img) YCCK JPEG (#425)'] = function (ctx, done) {
+  // This also provides coverage for CMYK JPEGs
+  var img = new Image()
+  img.onload = function () {
+    ctx.drawImage(img, 0, 0, 100, 100)
+    done(null)
+  }
+  img.onerror = done
+  img.src = imageSrc('ycck.jpg')
+}
+
+tests['drawImage(img) grayscale JPEG (#425)'] = function (ctx, done) {
+  var img = new Image()
+  img.onload = function () {
+    ctx.drawImage(img, 0, 0, 100, 100)
+    done(null)
+  }
+  img.onerror = done
+  img.src = imageSrc('grayscale.jpg')
+}
+
 tests['drawImage(img) svg'] = function (ctx, done) {
   var img = new Image()
   img.onload = function () {