fix(app): crop animated images on web with libwebp (#2947)

fluxer_app/rust/libfluxcore/src/formats.rs

@@ -16,6 +16,22 @@ pub fn is_animated_image_bytes(input: &[u8]) -> bool {
     false
 }
 
+pub fn sniff_image_format_bytes(input: &[u8]) -> u8 {
+    if is_png(input) {
+        1
+    } else if is_gif(input) {
+        2
+    } else if is_webp(input) {
+        3
+    } else if is_avif_file(input) {
+        4
+    } else if input.starts_with(&[0xff, 0xd8, 0xff]) {
+        5
+    } else {
+        0
+    }
+}
+
 fn is_gif(input: &[u8]) -> bool {
     input.starts_with(b"GIF89a") || input.starts_with(b"GIF87a")
 }
@@ -35,7 +51,16 @@ fn is_avif_file(input: &[u8]) -> bool {
 }
 
 fn has_avif_anim(input: &[u8]) -> bool {
-    is_avif_file(input) && &input[8..12] == b"avis"
+    if !is_avif_file(input) {
+        return false;
+    }
+    if &input[8..12] == b"avis" {
+        return true;
+    }
+    let box_end = read_u32_be(input, 0).map_or(0, |size| (size as usize).min(input.len()));
+    input
+        .get(16..box_end)
+        .is_some_and(|brands| brands.as_chunks::<4>().0.contains(b"avis"))
 }
 
 fn has_apng_actl(input: &[u8]) -> bool {
@@ -243,13 +268,53 @@ mod tests {
 
     #[test]
     fn detects_avif_sequence_brand() {
-        let avif = b"\x00\x00\x00\x18ftypavif\x00\x00\x00\x00avis";
-        assert!(!is_animated_image_bytes(avif));
+        let still = b"\x00\x00\x00\x18ftypavif\x00\x00\x00\x00mif1miaf";
+        assert!(!is_animated_image_bytes(still));
 
         let avis = b"\x00\x00\x00\x18ftypavis\x00\x00\x00\x00avif";
         assert!(is_animated_image_bytes(avis));
     }
 
+    #[test]
+    fn detects_avis_among_compatible_brands() {
+        let compat = b"\x00\x00\x00\x1cftypavif\x00\x00\x00\x00mif1avismsf1";
+        assert!(is_animated_image_bytes(compat));
+
+        let outside_ftyp = b"\x00\x00\x00\x14ftypavif\x00\x00\x00\x00mif1avis";
+        assert!(!is_animated_image_bytes(outside_ftyp));
+
+        let truncated = b"\x00\x00\x00\x40ftypavif\x00\x00\x00\x00mif1av";
+        assert!(!is_animated_image_bytes(truncated));
+    }
+
+    #[test]
+    fn sniffs_image_formats_from_magic_bytes() {
+        assert_eq!(sniff_image_format_bytes(b""), 0);
+        assert_eq!(sniff_image_format_bytes(b"<svg xmlns"), 0);
+        assert_eq!(
+            sniff_image_format_bytes(b"\x89PNG\r\n\x1a\n\0\0\0\rIHDR"),
+            1
+        );
+        assert_eq!(sniff_image_format_bytes(b"GIF89a\x01\x00"), 2);
+        assert_eq!(sniff_image_format_bytes(b"GIF87a\x01\x00"), 2);
+        assert_eq!(sniff_image_format_bytes(b"RIFF\x04\0\0\0WEBPVP8 "), 3);
+        assert_eq!(sniff_image_format_bytes(b"RIFF\x04\0\0\0WAVEfmt "), 0);
+        assert_eq!(
+            sniff_image_format_bytes(b"\x00\x00\x00\x18ftypavif\x00\x00\x00\x00"),
+            4
+        );
+        assert_eq!(
+            sniff_image_format_bytes(b"\x00\x00\x00\x18ftypavis\x00\x00\x00\x00"),
+            4
+        );
+        assert_eq!(
+            sniff_image_format_bytes(b"\x00\x00\x00\x18ftypheic\x00\x00\x00\x00"),
+            0
+        );
+        assert_eq!(sniff_image_format_bytes(b"\xff\xd8\xff\xe0\x00\x10JFIF"), 5);
+        assert_eq!(sniff_image_format_bytes(b"\xff\xd8"), 0);
+    }
+
     #[test]
     fn rejects_truncated_chunks_without_panicking() {
         assert!(!is_animated_image_bytes(

fluxer_app/rust/libfluxcore/src/lib.rs

@@ -5,8 +5,8 @@ mod rgba;
 mod zstd_frame;
 mod zstd_stream;
 
-use formats::is_animated_image_bytes;
-use rgba::{TransformRequest, crop_rotate_rgba_alloc};
+use formats::{is_animated_image_bytes, sniff_image_format_bytes};
+use rgba::{TransformRequest, crop_rotate_rgba_alloc, crop_rotate_rgba_into};
 use wasm_bindgen::prelude::*;
 
 #[wasm_bindgen]
@@ -40,6 +40,39 @@ pub fn crop_rotate_rgba_raw(
     .map_err(|error| JsValue::from_str(error.message()))
 }
 
+#[wasm_bindgen]
+#[allow(clippy::too_many_arguments)]
+pub fn crop_rotate_rgba_into_buffer(
+    input: &[u8],
+    output: &mut [u8],
+    src_width: u32,
+    src_height: u32,
+    x: u32,
+    y: u32,
+    width: u32,
+    height: u32,
+    rotation_deg: u32,
+    output_width: u32,
+    output_height: u32,
+) -> Result<(), JsValue> {
+    crop_rotate_rgba_into(
+        input,
+        output,
+        TransformRequest {
+            src_width,
+            src_height,
+            x,
+            y,
+            width,
+            height,
+            rotation_deg,
+            resize_width: output_width,
+            resize_height: output_height,
+        },
+    )
+    .map_err(|error| JsValue::from_str(error.message()))
+}
+
 #[wasm_bindgen]
 pub fn decompress_zstd_frame(input: &[u8]) -> Result<Vec<u8>, JsValue> {
     zstd_frame::decompress(input).map_err(zstd_error_to_js)
@@ -106,6 +139,11 @@ pub fn is_animated_image(input: &[u8]) -> bool {
     is_animated_image_bytes(input)
 }
 
+#[wasm_bindgen]
+pub fn sniff_image_format(input: &[u8]) -> u8 {
+    sniff_image_format_bytes(input)
+}
+
 fn optional_dimension_to_abi(value: Option<u32>) -> u32 {
     value.filter(|dimension| *dimension > 0).unwrap_or(u32::MAX)
 }

fluxer_app/rust/libfluxcore/src/rgba.rs

@@ -22,6 +22,7 @@ pub struct TransformRequest {
 pub enum TransformError {
     InvalidDimensions,
     InvalidRgbaLength,
+    InvalidOutputLength,
     EmptyCrop,
     EmptyTarget,
     ImageTooLarge,
@@ -33,6 +34,7 @@ impl TransformError {
         match self {
             Self::InvalidDimensions => "invalid RGBA dimensions",
             Self::InvalidRgbaLength => "RGBA input length does not match dimensions",
+            Self::InvalidOutputLength => "RGBA output length does not match target dimensions",
             Self::EmptyCrop => "Crop area is empty",
             Self::EmptyTarget => "Target dimensions are empty",
             Self::ImageTooLarge => "Image is too large to crop",
@@ -75,12 +77,7 @@ pub fn crop_rotate_rgba_alloc(
     input: &[u8],
     request: TransformRequest,
 ) -> Result<Vec<u8>, TransformError> {
-    let geometry = output_geometry(request)?;
-    let expected_len = rgba_byte_len(request.src_width, request.src_height, 0)?;
-    if input.len() != expected_len {
-        return Err(TransformError::InvalidRgbaLength);
-    }
-
+    let geometry = checked_geometry(input, request)?;
     let output_len = rgba_byte_len(
         geometry.target_width,
         geometry.target_height,
@@ -89,8 +86,45 @@ pub fn crop_rotate_rgba_alloc(
     let mut output = try_zeroed_vec(output_len)?;
     write_u32_le(&mut output, 0, geometry.target_width);
     write_u32_le(&mut output, 4, geometry.target_height);
+    write_transformed(
+        input,
+        &mut output[RGBA_RESULT_HEADER_BYTES..],
+        request,
+        geometry,
+    );
+    Ok(output)
+}
 
-    let dst = &mut output[RGBA_RESULT_HEADER_BYTES..];
+pub fn crop_rotate_rgba_into(
+    input: &[u8],
+    output: &mut [u8],
+    request: TransformRequest,
+) -> Result<(), TransformError> {
+    let geometry = checked_geometry(input, request)?;
+    if output.len() != rgba_byte_len(geometry.target_width, geometry.target_height, 0)? {
+        return Err(TransformError::InvalidOutputLength);
+    }
+    write_transformed(input, output, request, geometry);
+    Ok(())
+}
+
+fn checked_geometry(
+    input: &[u8],
+    request: TransformRequest,
+) -> Result<OutputGeometry, TransformError> {
+    let geometry = output_geometry(request)?;
+    if input.len() != rgba_byte_len(request.src_width, request.src_height, 0)? {
+        return Err(TransformError::InvalidRgbaLength);
+    }
+    Ok(geometry)
+}
+
+fn write_transformed(
+    input: &[u8],
+    dst: &mut [u8],
+    request: TransformRequest,
+    geometry: OutputGeometry,
+) {
     if geometry.target_width == geometry.base_width
         && geometry.target_height == geometry.base_height
     {
@@ -98,8 +132,6 @@ pub fn crop_rotate_rgba_alloc(
     } else {
         copy_rotated_with_nearest_resize(input, dst, request, geometry);
     }
-
-    Ok(output)
 }
 
 fn output_geometry(request: TransformRequest) -> Result<OutputGeometry, TransformError> {
@@ -463,6 +495,30 @@ mod tests {
         assert!(crop_rotate_rgba_alloc(&rgba(&[1, 2, 3, 4]), empty_target).is_ok());
     }
 
+    #[test]
+    fn into_writes_the_same_pixels_as_alloc() {
+        let input = rgba(&[1, 2, 3, 4, 5, 6]);
+        for rotation_deg in [0, 90, 180, 270] {
+            let mut transform = request(2, 3);
+            transform.rotation_deg = rotation_deg;
+            transform.resize_width = 5;
+            transform.resize_height = 4;
+            let expected = crop_rotate_rgba_alloc(&input, transform).unwrap();
+            let mut output = vec![0xaa; 5 * 4 * RGBA_BYTES_PER_PIXEL];
+            crop_rotate_rgba_into(&input, &mut output, transform).unwrap();
+            assert_eq!(output, payload(&expected));
+        }
+    }
+
+    #[test]
+    fn into_rejects_an_output_of_the_wrong_length() {
+        let mut output = vec![0; 3 * RGBA_BYTES_PER_PIXEL];
+        assert_eq!(
+            crop_rotate_rgba_into(&rgba(&[1, 2, 3, 4]), &mut output, request(2, 2)).unwrap_err(),
+            TransformError::InvalidOutputLength
+        );
+    }
+
     proptest! {
         #[test]
         fn identity_transform_preserves_pixels(width in 1u32..16, height in 1u32..16) {