LibGfx: Improve PNG encoder API somewhat

This is still far from ideal, but let's at least make it take a
Gfx::Bitmap const&.

Userland/Applications/PixelPaint/Image.cpp

@@ -155,11 +155,11 @@ void Image::export_bmp(const String& file_path)
 void Image::export_png(const String& file_path)
 {
  auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, m_size);
+ VERIFY(bitmap);
  GUI::Painter painter(*bitmap);
  paint_into(painter, { 0, 0, m_size.width(), m_size.height() });
 
- Gfx::PNGWriter png_writer;
- auto png = png_writer.write(bitmap);
+ auto png = Gfx::PNGWriter::encode(*bitmap);
  auto file = fopen(file_path.characters(), "wb");
  fwrite(png.data(), sizeof(u8), png.size(), file);
  fclose(file);

Userland/Libraries/LibGfx/PNGWriter.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Pierre Hoffmeister
+ * Copyright (c) 2021, Andreas Kling <[email protected]>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -24,17 +25,18 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include "PNGWriter.h"
 #include <AK/String.h>
 #include <LibCrypto/Checksum/CRC32.h>
+#include <LibGfx/Bitmap.h>
+#include <LibGfx/PNGWriter.h>
 
 namespace Gfx {
 
 class PNGChunk {
 public:
- PNGChunk(const String&);
- const Vector<u8>& data() const { return m_data; };
- const String& type() const { return m_type; };
+ explicit PNGChunk(String);
+ Vector<u8> const& data() const { return m_data; };
+ String const& type() const { return m_type; };
  void add_u8(u8);
  void add_u16_big(u16);
  void add_u32_big(u32);
@@ -51,8 +53,8 @@ class NonCompressibleBlock {
  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; }
+ u32 adler_s1() const { return m_adler_s1; }
+ u32 adler_s2() const { return m_adler_s2; }
 
 private:
  void add_block_to_chunk(PNGChunk&, bool);
@@ -63,7 +65,7 @@ class NonCompressibleBlock {
  u32 m_adler_s2 { 0 };
 };
 
-PNGChunk::PNGChunk(const String& type)
+PNGChunk::PNGChunk(String type)
  : m_type(move(type))
 {
 }
@@ -141,7 +143,7 @@ void NonCompressibleBlock::update_adler(u8 data)
  m_adler_s2 = (m_adler_s2 + m_adler_s1) % 65521;
 }
 
-void PNGWriter::add_chunk(const PNGChunk& png_chunk)
+void PNGWriter::add_chunk(PNGChunk const& png_chunk)
 {
  Vector<u8> combined;
  for (auto character : png_chunk.type()) {
@@ -185,7 +187,7 @@ void PNGWriter::add_IEND_chunk()
  add_chunk(png_chunk);
 }
 
-void PNGWriter::add_IDAT_chunk(const RefPtr<Bitmap> bitmap)
+void PNGWriter::add_IDAT_chunk(Gfx::Bitmap const& bitmap)
 {
  PNGChunk png_chunk { "IDAT" };
 
@@ -194,11 +196,11 @@ void PNGWriter::add_IDAT_chunk(const RefPtr<Bitmap> bitmap)
 
  NonCompressibleBlock non_compressible_block;
 
- for (int y = 0; y < bitmap->height(); ++y) {
+ 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);
+ 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);
@@ -213,16 +215,14 @@ void PNGWriter::add_IDAT_chunk(const RefPtr<Bitmap> bitmap)
  add_chunk(png_chunk);
 }
 
-ByteBuffer PNGWriter::write(const RefPtr<Bitmap> bitmap)
+ByteBuffer PNGWriter::encode(Gfx::Bitmap const& 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;
+ PNGWriter writer;
+ writer.add_png_header();
+ writer.add_IHDR_chunk(bitmap.width(), bitmap.height(), 8, 6, 0, 0, 0);
+ writer.add_IDAT_chunk(bitmap);
+ writer.add_IEND_chunk();
+ return ByteBuffer::copy(writer.m_data);
 }
 
 }

Userland/Libraries/LibGfx/PNGWriter.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Pierre Hoffmeister
+ * Copyright (c) 2021, Andreas Kling <[email protected]>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -26,24 +27,25 @@
 
 #pragma once
 
-#include <AK/String.h>
 #include <AK/Vector.h>
-#include <LibGfx/Bitmap.h>
+#include <LibGfx/Forward.h>
 
 namespace Gfx {
 
 class PNGChunk;
 
 class PNGWriter {
 public:
- ByteBuffer write(const RefPtr<Bitmap>);
+ static ByteBuffer encode(Gfx::Bitmap const&);
 
 private:
+ PNGWriter() { }
+
  Vector<u8> m_data;
- void add_chunk(const PNGChunk&);
+ void add_chunk(PNGChunk const&);
  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_IDAT_chunk(Gfx::Bitmap const&);
  void add_IEND_chunk();
 };
 

Userland/Utilities/shot.cpp

@@ -67,8 +67,7 @@ int main(int argc, char** argv)
  return 0;
  }
 
- Gfx::PNGWriter writer;
- auto encoded_bitmap = writer.write(bitmap);
+ auto encoded_bitmap = Gfx::PNGWriter::encode(*bitmap);
  if (encoded_bitmap.is_empty()) {
  warnln("Failed to encode PNG");
  return 1;