LibGfx: Implement image decoder for TinyVG (.tvg)

This adds a decoder for the TinyVG vector format (https://tinyvg.tech/). TinyVG is a very simple binary vector format, but it is good enough to represent a lot of SVGs, without needing the full web engine. The main use case for Serenity is for scalable icons (which .tvg easily handles).
2025-07-26 22:27:44 +00:00 · 2023-07-02 22:24:01 +01:00 · 2023-07-02 22:24:01 +01:00 · ae18186905
commit ae18186905
parent e7cddda7e1
4 changed files with 640 additions and 0 deletions
--- a/Userland/Libraries/LibGfx/ImageFormats/TinyVGLoader.h
+++ b/Userland/Libraries/LibGfx/ImageFormats/TinyVGLoader.h
@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/OwnPtr.h>
+#include <AK/Vector.h>
+#include <LibGfx/Color.h>
+#include <LibGfx/Forward.h>
+#include <LibGfx/ImageFormats/ImageDecoder.h>
+#include <LibGfx/PaintStyle.h>
+#include <LibGfx/Path.h>
+
+namespace Gfx {
+
+// Current recommended SVG to TVG conversion (without installing tools)
+// (FIXME: Implement our own converter!)
+// 1. (Optional) Convert strokes to fills
+//  * Only round joins/linecaps exist in TVG, so for other stroke kinds converting
+//    them to fills (that still beziers etc, so are scalable) works better.
+//  * This site can do that: https://iconly.io/tools/svg-convert-stroke-to-fill
+// 2. Scale your SVG's width/height to large size (e.g. 1024x?)
+//  * Current converters deal poorly with small values in paths.
+//  * This site can do that: https://www.iloveimg.com/resize-image/resize-svg
+//    (or just edit the viewbox if it has one).
+// 3. Convert the SVG to a TVG
+//  * This site can do that: https://svg-to-tvg-server.fly.dev/
+
+// Decoder from the "Tiny Vector Graphics" format (v1.0).
+// https://tinyvg.tech/download/specification.pdf
+
+class TinyVGDecodedImageData {
+public:
+    using Style = Variant<Color, NonnullRefPtr<SVGGradientPaintStyle>>;
+
+    struct DrawCommand {
+        Path path;
+        Optional<Style> fill {};
+        Optional<Style> stroke {};
+        float stroke_width { 0.0f };
+    };
+
+    ErrorOr<RefPtr<Gfx::Bitmap>> bitmap(IntSize size) const;
+
+    IntSize size() const
+    {
+        return m_size;
+    }
+
+    ReadonlySpan<DrawCommand> draw_commands() const
+    {
+        return m_draw_commands;
+    }
+
+    static ErrorOr<TinyVGDecodedImageData> decode(Stream& stream);
+
+private:
+    TinyVGDecodedImageData(IntSize size, Vector<DrawCommand> draw_commands)
+        : m_size(size)
+        , m_draw_commands(move(draw_commands))
+    {
+    }
+
+    IntSize m_size;
+    Vector<DrawCommand> m_draw_commands;
+};
+
+struct TinyVGLoadingContext {
+    ReadonlyBytes data;
+    OwnPtr<TinyVGDecodedImageData> decoded_image {};
+    RefPtr<Bitmap> bitmap {};
+};
+
+class TinyVGImageDecoderPlugin final : public ImageDecoderPlugin {
+public:
+    static bool sniff(ReadonlyBytes);
+    static ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> create(ReadonlyBytes);
+
+    virtual IntSize size() override;
+    virtual void set_volatile() override;
+    [[nodiscard]] virtual bool set_nonvolatile(bool&) override;
+    virtual ErrorOr<void> initialize() override;
+    virtual bool is_animated() override { return false; }
+    virtual size_t loop_count() override { return 0; }
+    virtual size_t frame_count() override { return 1; }
+    virtual size_t first_animated_frame_index() override { return 0; }
+    virtual ErrorOr<ImageFrameDescriptor> frame(size_t index, Optional<IntSize> ideal_size = {}) override;
+    virtual ErrorOr<Optional<ReadonlyBytes>> icc_data() override { return OptionalNone {}; };
+
+    virtual ~TinyVGImageDecoderPlugin() override = default;
+
+private:
+    TinyVGImageDecoderPlugin(ReadonlyBytes);
+
+    TinyVGLoadingContext m_context;
+};
+
+}