add formats parameter to Image.open to restrict list of formats attempting to read an image file

Tests/test_image.py

@@ -86,6 +86,26 @@ class TestImage:
         # with pytest.raises(MemoryError):
         #   Image.new("L", (1000000, 1000000))
 
+    def test_open_formats(self):
+        PNGFILE = "Tests/images/hopper.png"
+        JPGFILE = "Tests/images/hopper.jpg"
+
+        with pytest.raises(TypeError):
+            Image.open(PNGFILE, formats=123)
+
+        for formats in [["JPEG"], ("JPEG",)]:
+            with pytest.raises(UnidentifiedImageError):
+                Image.open(PNGFILE, formats=formats)
+
+            with Image.open(JPGFILE, formats=formats) as im:
+                assert im.mode == "RGB"
+                assert im.size == (128, 128)
+
+        for file in [PNGFILE, JPGFILE]:
+            with Image.open(file, formats=None) as im:
+                assert im.mode == "RGB"
+                assert im.size == (128, 128)
+
     def test_width_height(self):
         im = Image.new("RGB", (1, 2))
         assert im.width == 1

src/PIL/Image.py

@@ -2836,7 +2836,7 @@ def _decompression_bomb_check(size):
         )
 
 
-def open(fp, mode="r"):
+def open(fp, mode="r", formats=None):
     """
     Opens and identifies the given image file.
 
@@ -2867,6 +2867,11 @@ def open(fp, mode="r"):
             "Binary data must be used instead."
         )
 
+    if formats is None:
+        formats = ID
+    elif not isinstance(formats, (list, tuple)):
+        raise TypeError("formats must be a list or tuple")
+
     exclusive_fp = False
     filename = ""
     if isinstance(fp, Path):
@@ -2890,8 +2895,8 @@ def open(fp, mode="r"):
 
     accept_warnings = []
 
-    def _open_core(fp, filename, prefix):
+    def _open_core(fp, filename, prefix, formats):
-        for i in ID:
+        for i in formats:
             try:
                 factory, accept = OPEN[i]
                 result = not accept or accept(prefix)
@@ -2913,11 +2918,11 @@ def open(fp, mode="r"):
                 raise
         return None
 
-    im = _open_core(fp, filename, prefix)
+    im = _open_core(fp, filename, prefix, formats)
 
     if im is None:
         if init():
-            im = _open_core(fp, filename, prefix)
+            im = _open_core(fp, filename, prefix, formats)
 
     if im:
         im._exclusive_fp = exclusive_fp