https://github.com/chlumsky/easygifreader

A single-class C++ library for reading animated GIF files
https://github.com/chlumsky/easygifreader

Last synced: 3 months ago
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A single-class C++ library for reading animated GIF files

• Host: GitHub
• URL: https://github.com/chlumsky/easygifreader
• Owner: Chlumsky
• License: mit
• Created: 2021-10-28T14:31:58.000Z (over 3 years ago)
• Default Branch: master
• Last Pushed: 2024-06-09T10:01:25.000Z (8 months ago)
• Last Synced: 2024-06-09T11:21:56.119Z (8 months ago)
• Language: C++
• Homepage:
• Size: 11.7 KB
• Stars: 17
• Watchers: 3
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.txt

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README

        

# EasyGifReader

EasyGifReader is a single-class C++ library that aims to simplify reading an animated GIF file. It is built on top of and **depends on giflib**. While giflib does decode the binary format of the GIF file and converts it to structured data, there is still a lot left to do to make sense of this data before the animation can be presented, such as:

- Dealing with **indexed color** bitmaps and color maps.

- Compositing **partial frames** - ones that do not cover the entire area of the GIF.

- Correctly handling frame **disposal modes** - an optimization that allows each frame to use prior frames as its basis in multiple ways.

- Resolving **transparency**.

- Parsing **loop count** information from extension blocks.

Some of the data in a GIF file is ambiguous or interpreted inconsistently across software. In these cases, the library replicates the behavior of Google **Chrome**, which can be considered as the industry standard due to its status as the largest web browser. If you find a GIF file that behaves differently in Chrome, please report it as a bug.

## Installation

To use this library in your project, first make sure that **giflib** is available in the include path and is being linked. Then, simply add the files `EasyGifReader.h` and `EasyGifReader.cpp` to your C++ project.

## Usage

Using the `EasyGifReader` class is very straightforward and intuitive. The following example demonstrates how a GIF file can be loaded, and each of its frames inspected.

```c++

try {

    EasyGifReader gif = EasyGifReader::openFile("animation.gif");

    int frameCount = gif.frameCount();

    int width = gif.width();

    int height = gif.height();

    bool loop = gif.repeatsInfinitely();

    for (const EasyGifReader::Frame &frame : gif) {

        const EasyGifReader::PixelComponent *framePixels = frame.pixels();

        double frameDuration = frame.duration().seconds();

        // TODO display framePixels for frameDuration seconds

    }

} catch (EasyGifReader::Error gifError) {

    logError("Reading GIF file failed");

}

```

To clarify, `framePixels` is an array of `width*height` 32-bit pixels in the RGBA byte order. Due to limitations of the GIF format, the alpha component will always be either `0xFF` or `0x00`.