LibGfx/PortableFormat: Add PortableFormatWriter

Currently, the encoder only output ppm files, but it can easily be
extended to support both PBM and PGM.

Userland/Libraries/LibGfx/CMakeLists.txt

@@ -41,6 +41,7 @@ set(SOURCES
     PGMLoader.cpp
     PNGLoader.cpp
     PNGWriter.cpp
+    PortableFormatWriter.cpp
     PPMLoader.cpp
     Painter.cpp
     Palette.cpp

Userland/Libraries/LibGfx/PortableFormatWriter.cpp

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2023, Lucas Chollet <lucas.chollet@serenityos.org  >
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "PortableFormatWriter.h"
+#include <AK/String.h>
+
+namespace Gfx {
+
+ErrorOr<ByteBuffer> PortableFormatWriter::encode(Bitmap const& bitmap, Options options)
+{
+    ByteBuffer buffer;
+
+    // FIXME: Add support for PBM and PGM
+
+    TRY(add_header(buffer, options, bitmap.width(), bitmap.height(), 255));
+    TRY(add_pixels(buffer, options, bitmap));
+
+    return buffer;
+}
+
+ErrorOr<void> PortableFormatWriter::add_header(ByteBuffer& buffer, Options const& options, u32 width, u32 height, u32 maximal_value)
+{
+    TRY(buffer.try_append(TRY(String::formatted("P{}\n", options.format == Options::Format::ASCII ? "3"sv : "6"sv)).bytes()));
+    TRY(buffer.try_append(TRY(String::formatted("# {}\n", options.comment)).bytes()));
+    TRY(buffer.try_append(TRY(String::formatted("{} {}\n", width, height)).bytes()));
+    TRY(buffer.try_append(TRY(String::formatted("{}\n", maximal_value)).bytes()));
+
+    return {};
+}
+
+ErrorOr<void> PortableFormatWriter::add_pixels(ByteBuffer& buffer, Options const& options, Bitmap const& bitmap)
+{
+    for (int i = 0; i < bitmap.height(); ++i) {
+        for (int j = 0; j < bitmap.width(); ++j) {
+            auto color = bitmap.get_pixel(j, i);
+            if (options.format == Options::Format::ASCII) {
+                TRY(buffer.try_append(TRY(String::formatted("{} {} {}\t", color.red(), color.green(), color.blue())).bytes()));
+            } else {
+                TRY(buffer.try_append(color.red()));
+                TRY(buffer.try_append(color.green()));
+                TRY(buffer.try_append(color.blue()));
+            }
+        }
+        if (options.format == Options::Format::ASCII)
+            TRY(buffer.try_append('\n'));
+    }
+
+    return {};
+}
+
+}

Userland/Libraries/LibGfx/PortableFormatWriter.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2023, Lucas Chollet <lucas.chollet@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <LibGfx/Bitmap.h>
+
+namespace Gfx {
+
+// This is not a nested struct to work around https://llvm.org/PR36684
+struct PortableFormatWriterOptions {
+    enum class Format {
+        ASCII,
+        Raw,
+    };
+
+    Format format = Format::Raw;
+    StringView comment = "Generated with SerenityOS - LibGfx."sv;
+};
+
+class PortableFormatWriter {
+public:
+    using Options = PortableFormatWriterOptions;
+
+    static ErrorOr<ByteBuffer> encode(Bitmap const&, Options options = Options {});
+
+private:
+    PortableFormatWriter() = delete;
+
+    static ErrorOr<void> add_header(ByteBuffer&, Options const& options, u32 width, u32 height, u32 max_value);
+    static ErrorOr<void> add_pixels(ByteBuffer&, Options const& options, Bitmap const&);
+};
+
+}