LibGfx: adding a very simple PNG writer

With this patch it is possible to create PNG files. Only minimal options
are supported. The PNG is created with one big IDAT chunk containing
only non-compressible DEFLATE blocks.

Userland/Libraries/LibGfx/CMakeLists.txt

@@ -22,6 +22,7 @@ set(SOURCES
     PBMLoader.cpp
     PGMLoader.cpp
     PNGLoader.cpp
+    PNGWriter.cpp
     PPMLoader.cpp
     Point.cpp
     Rect.cpp

Userland/Libraries/LibGfx/PNGWriter.cpp

@@ -0,0 +1,228 @@
+/*
+ * Copyright (c) 2021, Pierre Hoffmeister
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "PNGWriter.h"
+#include <AK/String.h>
+#include <LibCrypto/Checksum/CRC32.h>
+
+namespace Gfx {
+
+class PNGChunk {
+public:
+    PNGChunk(const String&);
+    const Vector<u8>& data() const { return m_data; };
+    const String& type() const { return m_type; };
+    void add_u8(u8);
+    void add_u16_big(u16);
+    void add_u32_big(u32);
+    void add_u16_little(u16);
+    void add_u32_little(u32);
+
+private:
+    Vector<u8> m_data;
+    String m_type;
+};
+
+class NonCompressibleBlock {
+public:
+    void finalize(PNGChunk&);
+    void add_byte_to_block(u8 data, PNGChunk&);
+
+    u32 adler_s1() { return m_adler_s1; }
+    u32 adler_s2() { return m_adler_s2; }
+
+private:
+    void add_block_to_chunk(PNGChunk&, bool);
+    void update_adler(u8);
+    bool full() { return m_non_compressible_data.size() == 65535; }
+    Vector<u8> m_non_compressible_data;
+    u32 m_adler_s1 { 1 };
+    u32 m_adler_s2 { 0 };
+};
+
+PNGChunk::PNGChunk(const String& type)
+    : m_type(move(type))
+{
+}
+
+void PNGChunk::add_u8(u8 data)
+{
+    m_data.append(data);
+}
+
+void PNGChunk::add_u16_little(u16 data)
+{
+    m_data.append(data & 0xff);
+    m_data.append((data >> 8) & 0xff);
+}
+
+void PNGChunk::add_u32_little(u32 data)
+{
+    m_data.append(data & 0xff);
+    m_data.append((data >> 8) & 0xff);
+    m_data.append((data >> 16) & 0xff);
+    m_data.append((data >> 24) & 0xff);
+}
+
+void PNGChunk::add_u32_big(u32 data)
+{
+    m_data.append((data >> 24) & 0xff);
+    m_data.append((data >> 16) & 0xff);
+    m_data.append((data >> 8) & 0xff);
+    m_data.append(data & 0xff);
+}
+
+void PNGChunk::add_u16_big(u16 data)
+{
+    m_data.append((data >> 8) & 0xff);
+    m_data.append(data & 0xff);
+}
+
+void NonCompressibleBlock::add_byte_to_block(u8 data, PNGChunk& chunk)
+{
+    m_non_compressible_data.append(data);
+    update_adler(data);
+    if (full()) {
+        add_block_to_chunk(chunk, false);
+        m_non_compressible_data.clear();
+    }
+}
+
+void NonCompressibleBlock::add_block_to_chunk(PNGChunk& png_chunk, bool last)
+{
+    if (last) {
+        png_chunk.add_u8(1);
+    } else {
+        png_chunk.add_u8(0);
+    }
+
+    auto len = m_non_compressible_data.size();
+    auto nlen = ~len;
+
+    png_chunk.add_u16_little(len);
+    png_chunk.add_u16_little(nlen);
+
+    for (auto non_compressed_byte : m_non_compressible_data) {
+        png_chunk.add_u8(non_compressed_byte);
+    }
+}
+
+void NonCompressibleBlock::finalize(PNGChunk& chunk)
+{
+    add_block_to_chunk(chunk, true);
+}
+
+void NonCompressibleBlock::update_adler(u8 data)
+{
+    m_adler_s1 = (m_adler_s1 + data) % 65521;
+    m_adler_s2 = (m_adler_s2 + m_adler_s1) % 65521;
+}
+
+void PNGWriter::add_chunk(const PNGChunk& png_chunk)
+{
+    Vector<u8> combined;
+    for (auto character : png_chunk.type()) {
+        combined.append(character);
+    }
+    combined.append(png_chunk.data());
+
+    auto crc = BigEndian(Crypto::Checksum::CRC32({ (const u8*)combined.data(), combined.size() }).digest());
+    auto data_len = BigEndian(png_chunk.data().size());
+
+    ByteBuffer buf;
+    buf.append(&data_len, sizeof(u32));
+    buf.append(combined.data(), combined.size());
+    buf.append(&crc, sizeof(u32));
+
+    m_data.append(buf.data(), buf.size());
+}
+
+void PNGWriter::add_png_header()
+{
+    const u8 png_header[8] = { 0x89, 'P', 'N', 'G', 13, 10, 26, 10 };
+    m_data.append(png_header, sizeof(png_header));
+}
+
+void PNGWriter::add_IHDR_chunk(u32 width, u32 height, u8 bit_depth, u8 color_type, u8 compression_method, u8 filter_method, u8 interlace_method)
+{
+    PNGChunk png_chunk { "IHDR" };
+    png_chunk.add_u32_big(width);
+    png_chunk.add_u32_big(height);
+    png_chunk.add_u8(bit_depth);
+    png_chunk.add_u8(color_type);
+    png_chunk.add_u8(compression_method);
+    png_chunk.add_u8(filter_method);
+    png_chunk.add_u8(interlace_method);
+    add_chunk(png_chunk);
+}
+
+void PNGWriter::add_IEND_chunk()
+{
+    PNGChunk png_chunk { "IEND" };
+    add_chunk(png_chunk);
+}
+
+void PNGWriter::add_IDAT_chunk(const RefPtr<Bitmap> bitmap)
+{
+    PNGChunk png_chunk { "IDAT" };
+
+    u16 CMF_FLG = 0x81d;
+    png_chunk.add_u16_big(CMF_FLG);
+
+    NonCompressibleBlock non_compressible_block;
+
+    for (int y = 0; y < bitmap->height(); ++y) {
+        non_compressible_block.add_byte_to_block(0, png_chunk);
+
+        for (int x = 0; x < bitmap->width(); ++x) {
+            auto pixel = bitmap->get_pixel(x, y);
+            non_compressible_block.add_byte_to_block(pixel.red(), png_chunk);
+            non_compressible_block.add_byte_to_block(pixel.green(), png_chunk);
+            non_compressible_block.add_byte_to_block(pixel.blue(), png_chunk);
+            non_compressible_block.add_byte_to_block(pixel.alpha(), png_chunk);
+        }
+    }
+    non_compressible_block.finalize(png_chunk);
+
+    png_chunk.add_u16_big(non_compressible_block.adler_s2());
+    png_chunk.add_u16_big(non_compressible_block.adler_s1());
+
+    add_chunk(png_chunk);
+}
+
+ByteBuffer PNGWriter::write(const RefPtr<Bitmap> bitmap)
+{
+    add_png_header();
+    add_IHDR_chunk(bitmap->width(), bitmap->height(), 8, 6, 0, 0, 0);
+    add_IDAT_chunk(bitmap);
+    add_IEND_chunk();
+
+    ByteBuffer buf;
+    buf.append(m_data.data(), m_data.size());
+    return buf;
+}
+
+}

Userland/Libraries/LibGfx/PNGWriter.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2021, Pierre Hoffmeister
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Vector.h>
+#include <LibGfx/Bitmap.h>
+
+namespace Gfx {
+
+class PNGChunk;
+
+class PNGWriter {
+public:
+    ByteBuffer write(const RefPtr<Bitmap>);
+
+private:
+    Vector<u8> m_data;
+    void add_chunk(const PNGChunk&);
+    void add_png_header();
+    void add_IHDR_chunk(u32 width, u32 height, u8 bit_depth, u8 color_type, u8 compression_method, u8 filter_method, u8 interlace_method);
+    void add_IDAT_chunk(const RefPtr<Bitmap>);
+    void add_IEND_chunk();
+};
+
+}