blaind / webp-animation

A high-level Rust wrapper for decoding and encoding WebP animations

Hello world!

webp-animation's Issues

Null pointer dereference in test case `webp_data::tests::test_encoder`

I've been developing an experimental version of Miri that can execute foreign functions by interpreting LLVM bytecode.

Miri found the following error when executing the test webp_data::tests::test_encoder at version 0.9.0 of webp-animation.

error: Undefined Behavior: dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
   --> .../rust/library/core/src/slice/raw.rs:101:9
    |
101 |         &*ptr::slice_from_raw_parts(data, len)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
    = note: inside `std::slice::from_raw_parts::<'_, u8>` at .../rust/library/core/src/slice/raw.rs:101:9: 101:47
note: inside `webp_data::WebPData::as_slice`
   --> src/webp_data.rs:27:18
    |
27  |         unsafe { slice::from_raw_parts(self.data.bytes, self.data.size) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside `<webp_data::WebPData as std::ops::Deref>::deref`
   --> src/webp_data.rs:41:9
    |
41  |         self.as_slice()
    |         ^^^^^^^^^^^^^^^
note: inside `webp_data::tests::test_encoder`
   --> src/webp_data.rs:58:20
    |
58  |         assert_eq!(data.len(), 0);
    |                    ^^^^^^^^^^
note: inside closure
   --> src/webp_data.rs:56:23
    |
55  |     #[test]
    |     ------- in this procedural macro expansion
56  |     fn test_encoder() {
    | 

It seems like WebPData::new() does not actually initialize the WebPData struct to point to valid memory. In particular, here's where data is initialized in Rust:

let mut data = mem::zeroed();
webp::WebPDataInit(&mut data);
data

It seems like webp::WebPDataInit just zero-initializes the memory that it's passed:

static inline void WebPDataInit(WebPData* webp_data) {
  if (webp_data != ((void*)0)) {
    memset(webp_data, 0, sizeof(*webp_data));
  }
}

However, this shouldn't be necessary, since the memory being referenced has already been initialized by mem::zeroed() in Rust. Anyway, it seems like the implementation of WebPData::as_slice needs to account for the case when data is NULL.

Consider using `std::time::Duration` for timestamps

webp-animation/README.md

Lines 25 to 26 in abe7664

	Functional Goals:
	* Easy-to-use API that looks like Rust

The type i32 is used for timestamps in a lot of places.

Do you think you could switch to using Rust's std::time::Duration for timestamps instead?

This would make the interface look more like Rust and less like C, and it would have saved me some docs reading.

Please support ColorMode::Rgb (no alpha channel)

Hi!

My input is in RGB format, with no alpha channel.

To encode this I'd like to specify ColorMode::Rgb, but the currently supported color modes have alpha channels:

webp-animation/src/lib.rs

Lines 40 to 48 in abe7664

	/// Color Mode that configures the output type of [`Decoder`] [`Frame`]'s
	#[derive(Copy, Clone, PartialEq, Debug)]
	pub enum ColorMode {
	/// Rgba (red, green, blue, alpha)
	Rgba,
	/// Bgra (blue, green, red, alpha)
	Bgra,
	// what about MODE_rgbA and MODE_bgrA ?
	}

Could you please add an RGB ColorMode?

How to encode a looping animation?

I want to make my animation run in a loop.

But searching for "loop" in here doesn't give me any hints on how to do that.

In the C library looping is part of the encoder options.

Frame Rate

After decode an animated webp file I need to encode it to gif with another libray. It works but I dont know the frame rate and new gif has different speed.

Is there a way to get frame rates? If there is no such a feature it would be very useful.

Thank you for this amazing library.