Add a basic DDS image plugin

Only supports DXT1 and DXT5 for now.
The pixel formats ideally should be supported in decode.c instead,
but for now this is good enough.

Fixes #252

CHANGES.rst

@@ -6,6 +6,8 @@ Changelog (Pillow)
 
 - Fix incorrect conditional in encode.c #1638
   [manisandro]
+- Add a basic read-only DDS plugin #252
+  [jleclanche]
 
 3.1.0 (2016-01-04)
 ------------------

PIL/DdsImagePlugin.py

@@ -0,0 +1,253 @@
+"""
+A Pillow loader for .dds files (S3TC-compressed aka DXTC)
+Jerome Leclanche <jerome@leclan.ch>
+
+Documentation:
+  http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt
+
+The contents of this file are hereby released in the public domain (CC0)
+Full text of the CC0 license:
+  https://creativecommons.org/publicdomain/zero/1.0/
+"""
+
+import struct
+from io import BytesIO
+from PIL import Image, ImageFile
+
+
+# Magic ("DDS ")
+DDS_MAGIC = 0x20534444
+
+# DDS flags
+DDSD_CAPS = 0x1
+DDSD_HEIGHT = 0x2
+DDSD_WIDTH = 0x4
+DDSD_PITCH = 0x8
+DDSD_PIXELFORMAT = 0x1000
+DDSD_MIPMAPCOUNT = 0x20000
+DDSD_LINEARSIZE = 0x80000
+DDSD_DEPTH = 0x800000
+
+# DDS caps
+DDSCAPS_COMPLEX = 0x8
+DDSCAPS_TEXTURE = 0x1000
+DDSCAPS_MIPMAP = 0x400000
+
+DDSCAPS2_CUBEMAP = 0x200
+DDSCAPS2_CUBEMAP_POSITIVEX = 0x400
+DDSCAPS2_CUBEMAP_NEGATIVEX = 0x800
+DDSCAPS2_CUBEMAP_POSITIVEY = 0x1000
+DDSCAPS2_CUBEMAP_NEGATIVEY = 0x2000
+DDSCAPS2_CUBEMAP_POSITIVEZ = 0x4000
+DDSCAPS2_CUBEMAP_NEGATIVEZ = 0x8000
+DDSCAPS2_VOLUME = 0x200000
+
+# Pixel Format
+DDPF_ALPHAPIXELS = 0x1
+DDPF_ALPHA = 0x2
+DDPF_FOURCC = 0x4
+DDPF_PALETTEINDEXED8 = 0x20
+DDPF_RGB = 0x40
+DDPF_LUMINANCE = 0x20000
+
+
+# dds.h
+
+DDS_FOURCC = DDPF_FOURCC
+DDS_RGB = DDPF_RGB
+DDS_RGBA = DDPF_RGB | DDPF_ALPHAPIXELS
+DDS_LUMINANCE = DDPF_LUMINANCE
+DDS_LUMINANCEA = DDPF_LUMINANCE | DDPF_ALPHAPIXELS
+DDS_ALPHA = DDPF_ALPHA
+DDS_PAL8 = DDPF_PALETTEINDEXED8
+
+DDS_HEADER_FLAGS_TEXTURE = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT
+DDS_HEADER_FLAGS_MIPMAP = DDSD_MIPMAPCOUNT
+DDS_HEADER_FLAGS_VOLUME = DDSD_DEPTH
+DDS_HEADER_FLAGS_PITCH = DDSD_PITCH
+DDS_HEADER_FLAGS_LINEARSIZE = DDSD_LINEARSIZE
+
+DDS_HEIGHT = DDSD_HEIGHT
+DDS_WIDTH = DDSD_WIDTH
+
+DDS_SURFACE_FLAGS_TEXTURE = DDSCAPS_TEXTURE
+DDS_SURFACE_FLAGS_MIPMAP = DDSCAPS_COMPLEX | DDSCAPS_MIPMAP
+DDS_SURFACE_FLAGS_CUBEMAP = DDSCAPS_COMPLEX
+
+DDS_CUBEMAP_POSITIVEX = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEX
+DDS_CUBEMAP_NEGATIVEX = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEX
+DDS_CUBEMAP_POSITIVEY = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEY
+DDS_CUBEMAP_NEGATIVEY = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEY
+DDS_CUBEMAP_POSITIVEZ = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEZ
+DDS_CUBEMAP_NEGATIVEZ = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEZ
+
+
+# DXT1
+DXT1_FOURCC = 0x31545844
+
+# DXT3
+DXT3_FOURCC = 0x33545844
+
+# DXT5
+DXT5_FOURCC = 0x35545844
+
+
+def decode565(bits):
+    a = ((bits >> 11) & 0x1f) << 3
+    b = ((bits >> 5) & 0x3f) << 2
+    c = (bits & 0x1f) << 3
+    return a, b, c
+
+
+def _c2a(a, b):
+    return (2 * a + b) // 3
+
+def _c2b(a, b):
+    return (a + b) // 2
+
+def _c3(a, b):
+    return (2 * b + a) // 3
+
+
+def dxt1(data, width, height):
+    ret = bytearray(4 * width * height)
+
+    for y in range(0, height, 4):
+        for x in range(0, width, 4):
+            color0, color1, bits = struct.unpack("<HHI", data.read(8))
+
+            r0, g0, b0 = decode565(color0)
+            r1, g1, b1 = decode565(color1)
+
+            # Decode this block into 4x4 pixels
+            for j in range(4):
+                for i in range(4):
+                    # get next control op and generate a pixel
+                    control = bits & 3
+                    bits = bits >> 2
+                    if control == 0:
+                        r, g, b = r0, g0, b0
+                    elif control == 1:
+                        r, g, b = r1, g1, b1
+                    elif control == 2:
+                        if color0 > color1:
+                            r, g, b = _c2a(r0, r1), _c2a(g0, g1), _c2a(b0, b1)
+                        else:
+                            r, g, b = _c2b(r0, r1), _c2b(g0, g1), _c2b(b0, b1)
+                    elif control == 3:
+                        if color0 > color1:
+                            r, g, b = _c3(r0, r1), _c3(g0, g1), _c3(b0, b1)
+                        else:
+                            r, g, b = 0, 0, 0
+
+                    idx = 4 * ((y + j) * width + (x + i))
+                    ret[idx:idx+4] = bytes([r, g, b, 0xff])
+
+    return bytes(ret)
+
+
+def _dxtc_alpha(a0, a1, ac0, ac1, ai):
+    if ai <= 12:
+        ac = (ac0 >> ai) & 7
+    elif ai == 15:
+        ac = (ac0 >> 15) | ((ac1 << 1) & 6)
+    else:
+        ac = (ac1 >> (ai - 16)) & 7
+
+    if ac == 0:
+        alpha = a0
+    elif ac == 1:
+        alpha = a1
+    elif a0 > a1:
+        alpha = ((8 - ac) * a0 + (ac - 1) * a1) // 7
+    elif ac == 6:
+        alpha = 0
+    elif ac == 7:
+        alpha = 0xff
+    else:
+        alpha = ((6 - ac) * a0 + (ac - 1) * a1) // 5
+
+    return alpha
+
+
+def dxt5(data, width, height):
+    ret = bytearray(4 * width * height)
+
+    for y in range(0, height, 4):
+        for x in range(0, width, 4):
+            a0, a1, ac0, ac1, c0, c1, code = struct.unpack("<2BHI2HI", data.read(16))
+
+            r0, g0, b0 = decode565(c0)
+            r1, g1, b1 = decode565(c1)
+
+            for j in range(4):
+                for i in range(4):
+                    ai = 3 * (4 * j + i)
+                    alpha = _dxtc_alpha(a0, a1, ac0, ac1, ai)
+
+                    cc = (code >> 2 * (4 * j + i)) & 3
+                    if cc == 0:
+                        r, g, b = r0, g0, b0
+                    elif cc == 1:
+                        r, g, b = r1, g1, b1
+                    elif cc == 2:
+                        r, g, b = _c2a(r0, r1), _c2a(g0, g1), _c2a(b0, b1)
+                    elif cc == 3:
+                        r, g, b = _c3(r0, r1), _c3(g0, g1), _c3(b0, b1)
+
+                    idx = 4 * ((y + j) * width + (x + i))
+                    ret[idx:idx+4] = bytes([r, g, b, alpha])
+
+    return bytes(ret)
+
+
+class DdsImageFile(ImageFile.ImageFile):
+    format = "DDS"
+    format_description = "DirectDraw Surface"
+
+    def _open(self):
+        magic, header_size = struct.unpack("<II", self.fp.read(8))
+        if header_size != 124:
+            raise IOError("Unsupported header size %r" % (header_size))
+        header = BytesIO(self.fp.read(header_size - 4))
+
+        flags, height, width = struct.unpack("<3I", header.read(12))
+        self.size = (width, height)
+        self.mode = "RGBA"
+
+        pitch, depth, mipmaps = struct.unpack("<3I", header.read(12))
+        reserved = struct.unpack("<11I", header.read(44))
+
+        # pixel format
+        pfsize, pfflags = struct.unpack("<2I", header.read(8))
+        fourcc = header.read(4)
+        bitcount, rmask, gmask, bmask, amask = struct.unpack("<5I", header.read(20))
+
+        self.tile = [
+            ("raw", (0, 0) + self.size, 0, (self.mode, 0, 1))
+        ]
+
+        if fourcc == b"DXT1":
+            self.pixel_format = "DXT1"
+            codec = dxt1
+        elif fourcc == b"DXT5":
+            self.pixel_format = "DXT5"
+            codec = dxt5
+        else:
+            raise NotImplementedError("Unimplemented pixel format %r" % (fourcc))
+
+        decoded_data = codec(self.fp, self.width, self.height)
+
+        self.fp.close()
+        self.fp = BytesIO(decoded_data)
+
+    def load_seek(self, pos):
+        pass
+
+
+def _validate(prefix):
+    return prefix[:4] == b"DDS "
+
+
+Image.register_open(DdsImageFile.format, DdsImageFile, _validate)
+Image.register_extension(DdsImageFile.format, ".dds")

PIL/__init__.py

@@ -18,6 +18,7 @@ _plugins = ['BmpImagePlugin',
             'BufrStubImagePlugin',
             'CurImagePlugin',
             'DcxImagePlugin',
+            'DdsImagePlugin',
             'EpsImagePlugin',
             'FitsStubImagePlugin',
             'FliImagePlugin',

docs/handbook/image-file-formats.rst

@@ -633,6 +633,16 @@ is commonly used in fax applications. The DCX decoder can read files containing
 When the file is opened, only the first image is read. You can use
 :py:meth:`~file.seek` or :py:mod:`~PIL.ImageSequence` to read other images.
 
+
+DDS
+^^^
+
+DDS is a popular container texture format used in video games and natively
+supported by DirectX.
+Currently, only DXT1 and DXT5 pixel formats are supported and only in ``RGBA``
+mode.
+
+
 FLI, FLC
 ^^^^^^^^