Added convert_mode param when saving

Tests/test_file_gif.py

@@ -554,6 +554,16 @@ def test_save_I(self):
         reloaded = Image.open(out)
         self.assert_image_equal(reloaded.convert('L'), im.convert('L'))
 
+    def test_save_wrong_modes(self):
+        out = BytesIO()
+        for mode in ['CMYK']:
+            img = Image.new(mode, (20, 20))
+            self.assertRaises(ValueError, img.save, out, "GIF")
+
+        for mode in ['CMYK', 'LA']:
+            img = Image.new(mode, (20, 20))
+            img.save(out, "GIF", convert_mode=True)
+
     def test_getdata(self):
         # test getheader/getdata against legacy values
         # Create a 'P' image with holes in the palette

Tests/test_file_jpeg.py

@@ -509,10 +509,22 @@ def test_save_correct_modes(self):
     def test_save_wrong_modes(self):
         # ref https://github.com/python-pillow/Pillow/issues/2005
         out = BytesIO()
-        for mode in ['LA', 'La', 'RGBA', 'RGBa', 'P']:
+        for mode in ['LA', 'La', 'RGBA', 'RGBa', 'P', 'I']:
             img = Image.new(mode, (20, 20))
             self.assertRaises(IOError, img.save, out, "JPEG")
 
+        for mode in ['LA', 'RGBA', 'P', 'I']:
+            img = Image.new(mode, (20, 20))
+            img.save(out, "JPEG", convert_mode=True)
+
+        img = Image.open('Tests/images/pil123rgba.png')
+        temp_file = self.tempfile("temp.jpg")
+        img.save(temp_file, convert_mode=True, fill_color='red')
+
+        reloaded = Image.open(temp_file)
+        target = Image.open('Tests/images/pil123rgba_red.jpg')
+        self.assert_image_similar(reloaded, target, 4)
+
     def test_save_tiff_with_dpi(self):
         # Arrange
         outfile = self.tempfile("temp.tif")

Tests/test_file_png.py

@@ -227,6 +227,13 @@ def test_load_transparent_rgb(self):
         # image has 876 transparent pixels
         self.assertEqual(im.getchannel('A').getcolors()[0][0], 876)
 
+    def test_save_CMYK(self):
+        out = BytesIO()
+        img = Image.new('CMYK', (20, 20))
+        self.assertRaises(IOError, img.save, out, "PNG")
+
+        img.save(out, "PNG", convert_mode=True)
+
     def test_save_p_transparent_palette(self):
         in_file = "Tests/images/pil123p.png"
         im = Image.open(in_file)

Tests/test_file_webp.py

@@ -2,6 +2,8 @@
 
 from PIL import Image
 
+from io import BytesIO
+
 try:
     from PIL import _webp
     HAVE_WEBP = True
@@ -44,6 +46,12 @@ def test_read_rgb(self):
         target = target.convert(self.rgb_mode)
         self.assert_image_similar(image, target, 20.0)
 
+    def test_save_convert_mode(self):
+        out = BytesIO()
+        for mode in ['CMYK', 'I', 'L', 'LA', 'P']:
+            img = Image.new(mode, (20, 20))
+            img.save(out, "WEBP", convert_mode=True)
+
     def test_write_rgb(self):
         """
         Can we write a RGB mode file to webp without error.

Tests/test_image.py

@@ -1,6 +1,6 @@
 from helper import unittest, PillowTestCase, hopper
 
-from PIL import Image
+from PIL import Image, TiffImagePlugin
 from PIL._util import py3
 import os
 
@@ -324,6 +324,14 @@ def test_registered_extensions(self):
         for ext in ['.cur', '.icns', '.tif', '.tiff']:
             self.assertIn(ext, extensions)
 
+    def test_no_convert_mode(self):
+        self.assertTrue(not hasattr(TiffImagePlugin, '_convert_mode'))
+
+        temp_file = self.tempfile("temp.jpg")
+
+        im = hopper()
+        im.save(temp_file, convert_mode=True)
+
     def test_effect_mandelbrot(self):
         # Arrange
         size = (512, 512)

src/PIL/GifImagePlugin.py

@@ -798,6 +798,13 @@ def write(self, data):
     return fp.data
 
 
+def _convert_mode(im):
+    return {
+        'LA':'P',
+        'CMYK':'RGB'
+    }.get(im.mode)
+
+
 # --------------------------------------------------------------------
 # Registry
 

src/PIL/Image.py

@@ -1903,12 +1903,6 @@ def save(self, fp, format=None, **params):
         # may mutate self!
         self.load()
 
-        save_all = False
-        if 'save_all' in params:
-            save_all = params.pop('save_all')
-        self.encoderinfo = params
-        self.encoderconfig = ()
-
         preinit()
 
         ext = os.path.splitext(filename)[1].lower()
@@ -1923,11 +1917,23 @@ def save(self, fp, format=None, **params):
 
         if format.upper() not in SAVE:
             init()
+        save_all = False
+        if 'save_all' in params:
+            save_all = params.pop('save_all')
         if save_all:
             save_handler = SAVE_ALL[format.upper()]
         else:
             save_handler = SAVE[format.upper()]
 
+        if params.get('convert_mode'):
+            plugin = sys.modules[save_handler.__module__]
+            convertedIm = self._convert_mode(plugin, params)
+            if convertedIm:
+                return convertedIm.save(fp, format, **params)
+
+        self.encoderinfo = params
+        self.encoderconfig = ()
+
         if open_fp:
             if params.get('append', False):
                 fp = builtins.open(filename, "r+b")
@@ -1943,6 +1949,37 @@ def save(self, fp, format=None, **params):
             if open_fp:
                 fp.close()
 
+    def _convert_mode(self, plugin, params):
+        if not hasattr(plugin, '_convert_mode'):
+            return
+        new_mode = plugin._convert_mode(self)
+        if self.mode == 'LA' and new_mode == 'P':
+            alpha = self.getchannel('A')
+            # Convert the image into P mode but only use 255 colors
+            # in the palette out of 256.
+            im = self.convert('L') \
+                .convert('P', palette=ADAPTIVE, colors=255)
+            # Set all pixel values below 128 to 255, and the rest to 0.
+            mask = eval(alpha, lambda px: 255 if px < 128 else 0)
+            # Paste the color of index 255 and use alpha as a mask.
+            im.paste(255, mask)
+            # The transparency index is 255.
+            im.info['transparency'] = 255
+            return im
+
+        elif self.mode == 'I':
+            im = self.point([i//256 for i in range(65536)], 'L')
+            return im.convert(new_mode) if new_mode != 'L' else im
+
+        elif self.mode in ('RGBA', 'LA') and new_mode in ('RGB', 'L'):
+            fill_color = params.get('fill_color', 'white')
+            background = new(new_mode, self.size, fill_color)
+            background.paste(self, self.getchannel('A'))
+            return background
+
+        elif new_mode:
+            return self.convert(new_mode)
+
     def seek(self, frame):
         """
         Seeks to the given frame in this sequence file. If you seek

src/PIL/JpegImagePlugin.py

@@ -792,6 +792,23 @@ def jpeg_factory(fp=None, filename=None):
     return im
 
 
+def _convert_mode(im):
+    mode = im.mode
+    if mode == 'P':
+        new_mode = 'RGB'
+        try:
+            if 'A' in im.im.getpalettemode():
+                new_mode = 'RGBA'
+        except ValueError:
+            pass
+        return new_mode
+    return {
+        'RGBA':'RGB',
+        'LA':'L',
+        'I':'L'
+    }.get(mode)
+
+
 # -------------------------------------------------------------------q-
 # Registry stuff
 

src/PIL/PngImagePlugin.py

@@ -859,6 +859,12 @@ def append(fp, cid, *data):
     return fp.data
 
 
+def _convert_mode(im):
+    return {
+        'CMYK':'RGB'
+    }.get(im.mode)
+
+
 # --------------------------------------------------------------------
 # Registry
 

src/PIL/WebPImagePlugin.py

@@ -308,6 +308,25 @@ def _save(im, fp, filename):
     fp.write(data)
 
 
+def _convert_mode(im):
+    mode = im.mode
+    if mode == 'P':
+        new_mode = 'RGB'
+        try:
+            if 'A' in im.im.getpalettemode():
+                new_mode = 'RGBA'
+        except ValueError:
+            pass
+        return new_mode
+    return {
+        # Pillow doesn't support L modes for webp for now.
+        'L':'RGB',
+        'LA':'RGBA',
+        'I':'RGB',
+        'CMYK':'RGB'
+    }.get(mode)
+
+
 Image.register_open(WebPImageFile.format, WebPImageFile, _accept)
 Image.register_save(WebPImageFile.format, _save)
 if _webp.HAVE_WEBPANIM: