Thumbnails: refactor extraction to use one code-path for all platforms

Thumbnail extraction now shares code between Linux/Windows,
allowing thumbnails from Zstd compressed blend files to be extracted.

The main logic is placed in blendthumb_extract.cc and is built as static
library. For windows there is DLL which is registered during blender
install and which then reads and generates thumbnails.

For other platforms there is blender-thumbnailer executable file which
takes blend file as an input and generates PNG file. As a result
Python script blender-thumbnailer.py is no longer needed.

The thumbnail extractor shares the same code-path as Blenders file
reading, so there is no need to duplicate any file reading logic.
This means reading compressed blend files is supported (broken since
the recent move Zstd compression - D5799).

This resolves T63736.

Contributors:

- @alausic original patch.
- @LazyDodo windows fixes/support.
- @campbellbarton general fixes/update.
- @lukasstockner97 Zstd support.

Reviewed By: sybren, mont29, LazyDodo, campbellbarton

Ref D6408

1 files changed, 158 insertions, 0 deletions

diff --git a/source/blender/blendthumb/src/blendthumb_png.cc b/source/blender/blendthumb/src/blendthumb_png.cc
new file mode 100644
index 00000000000..d8156150078
--- /dev/null
+++ b/source/blender/blendthumb/src/blendthumb_png.cc
@@ -0,0 +1,158 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2008 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup blendthumb
+ *
+ * Expose #blendthumb_create_png_data_from_thumb that creates the PNG data
+ * but does not write it to a file.
+ */
+
+#include <cstring>
+#include <optional>
+#include <zlib.h>
+
+#include "blendthumb.hh"
+
+#include "BLI_endian_defines.h"
+#include "BLI_endian_switch.h"
+#include "BLI_vector.hh"
+
+static void png_extend_native_int32(blender::Vector<uint8_t> &output, int32_t data)
+{
+  if (ENDIAN_ORDER == L_ENDIAN) {
+    BLI_endian_switch_int32(&data);
+  }
+  output.extend_unchecked(blender::Span((uint8_t *)&data, 4));
+}
+
+/** The number of bytes each chunk uses on top of the data that's written. */
+#define PNG_CHUNK_EXTRA 12
+
+static void png_chunk_create(blender::Vector<uint8_t> &output,
+                             const uint32_t tag,
+                             const blender::Vector<uint8_t> &data)
+{
+  uint32_t crc = crc32(0, nullptr, 0);
+  crc = crc32(crc, (uint8_t *)&tag, sizeof(tag));
+  crc = crc32(crc, (uint8_t *)data.data(), data.size());
+
+  png_extend_native_int32(output, data.size());
+  output.extend_unchecked(blender::Span((uint8_t *)&tag, sizeof(tag)));
+  output.extend_unchecked(data);
+  png_extend_native_int32(output, crc);
+}
+
+static blender::Vector<uint8_t> filtered_rows_from_thumb(const Thumbnail *thumb)
+{
+  /* In the image data sent to the compression step, each scan-line is preceded by a filter type
+   * byte containing the numeric code of the filter algorithm used for that scan-line. */
+  const size_t line_size = thumb->width * 4;
+  blender::Vector<uint8_t> filtered{};
+  size_t final_size = thumb->height * (line_size + 1);
+  filtered.reserve(final_size);
+  for (int i = 0; i < thumb->height; i++) {
+    filtered.append_unchecked(0x00);
+    filtered.extend_unchecked(blender::Span(&thumb->data[i * line_size], line_size));
+  }
+  BLI_assert(final_size == filtered.size());
+  return filtered;
+}
+
+static std::optional<blender::Vector<uint8_t>> zlib_compress(const blender::Vector<uint8_t> &data)
+{
+  unsigned long uncompressed_size = data.size();
+  uLongf compressed_size = compressBound(uncompressed_size);
+
+  blender::Vector<uint8_t> compressed(compressed_size, 0x00);
+
+  int return_value = compress2((uchar *)compressed.data(),
+                               &compressed_size,
+                               (uchar *)data.data(),
+                               uncompressed_size,
+                               Z_NO_COMPRESSION);
+  if (return_value != Z_OK) {
+    /* Something went wrong with compression of data. */
+    return std::nullopt;
+  }
+  compressed.resize(compressed_size);
+  return compressed;
+}
+
+std::optional<blender::Vector<uint8_t>> blendthumb_create_png_data_from_thumb(
+    const Thumbnail *thumb)
+{
+  if (thumb->data.is_empty()) {
+    return std::nullopt;
+  }
+
+  /* Create `IDAT` chunk data. */
+  blender::Vector<uint8_t> image_data{};
+  {
+    auto image_data_opt = zlib_compress(filtered_rows_from_thumb(thumb));
+    if (image_data_opt == std::nullopt) {
+      return std::nullopt;
+    }
+    image_data = *image_data_opt;
+  }
+
+  /* Create the IHDR chunk data. */
+  blender::Vector<uint8_t> ihdr_data{};
+  {
+    const size_t ihdr_data_final_size = 4 + 4 + 5;
+    ihdr_data.reserve(ihdr_data_final_size);
+    png_extend_native_int32(ihdr_data, thumb->width);
+    png_extend_native_int32(ihdr_data, thumb->height);
+    ihdr_data.extend_unchecked({
+        0x08, /* Bit Depth. */
+        0x06, /* Color Type. */
+        0x00, /* Compression method. */
+        0x00, /* Filter method. */
+        0x00, /* Interlace method. */
+    });
+    BLI_assert((size_t)ihdr_data.size() == ihdr_data_final_size);
+  }
+
+  /* Join it all together to create a PNG image. */
+  blender::Vector<uint8_t> png_buf{};
+  {
+    const size_t png_buf_final_size = (
+        /* Header. */
+        8 +
+        /* `IHDR` chunk. */
+        (ihdr_data.size() + PNG_CHUNK_EXTRA) +
+        /* `IDAT` chunk. */
+        (image_data.size() + PNG_CHUNK_EXTRA) +
+        /* `IEND` chunk. */
+        PNG_CHUNK_EXTRA);
+
+    png_buf.reserve(png_buf_final_size);
+
+    /* This is the standard PNG file header. Every PNG file starts with it. */
+    png_buf.extend_unchecked({0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A});
+
+    png_chunk_create(png_buf, MAKE_ID('I', 'H', 'D', 'R'), ihdr_data);
+    png_chunk_create(png_buf, MAKE_ID('I', 'D', 'A', 'T'), image_data);
+    png_chunk_create(png_buf, MAKE_ID('I', 'E', 'N', 'D'), {});
+
+    BLI_assert((size_t)png_buf.size() == png_buf_final_size);
+  }
+
+  return png_buf;
+}