Struct WasmCogViewer 

pub struct WasmCogViewer { /* private fields */ }

WASM-compatible COG (Cloud Optimized GeoTIFF) viewer

This is the basic COG viewer for browser-based geospatial data visualization. It provides simple access to COG metadata and tile reading functionality.

Features

• Efficient tile-based access to large GeoTIFF files
• Support for multi-band imagery
• Overview/pyramid level access for different zoom levels
• CORS-compatible HTTP range request support
• Automatic TIFF header parsing
• GeoTIFF metadata extraction (CRS, geotransform, etc.)

Performance

The viewer uses HTTP range requests to fetch only the required portions of the file, making it efficient for large files. However, for production use cases with caching and advanced features, consider using AdvancedCogViewer instead.

Example

const viewer = new WasmCogViewer();
await viewer.open('<https://example.com/image.tif>');
console.log(`Size: ${viewer.width()}x${viewer.height()}`);
const tile = await viewer.read_tile_as_image_data(0, 0, 0);

Implementations

impl WasmCogViewer

pub fn new() -> Self

Creates a new COG viewer

pub async fn open(&mut self, url: &str) -> Result<(), JsValue>

Opens a COG file from a URL

This method performs the following operations:

1. Sends a HEAD request to determine file size and range support
2. Fetches the TIFF header to validate format
3. Parses IFD (Image File Directory) to extract metadata
4. Extracts GeoTIFF tags for coordinate system information
5. Counts overview levels for multi-resolution support

Arguments

• url - The URL of the COG file to open. Must support HTTP range requests for optimal performance. CORS must be properly configured.

Returns

Returns Ok(()) on success, or a JavaScript error on failure.

Errors

This method can fail for several reasons:

• Network errors (no connection, timeout, etc.)
• HTTP errors (404, 403, 500, etc.)
• CORS errors (missing headers)
• Invalid TIFF format
• Unsupported TIFF variant

Example

const viewer = new WasmCogViewer();
try {
    await viewer.open('<https://example.com/landsat.tif>');
    console.log('Successfully opened COG');
} catch (error) {
    console.error('Failed to open:', error);
}

pub fn width(&self) -> u64

Returns the image width

pub fn height(&self) -> u64

Returns the image height

pub fn tile_width(&self) -> u32

Returns the tile width

pub fn tile_height(&self) -> u32

Returns the tile height

pub fn band_count(&self) -> u32

Returns the number of bands

pub fn overview_count(&self) -> usize

Returns the number of overview levels

pub fn epsg_code(&self) -> Option<u32>

Returns the EPSG code if available

pub fn url(&self) -> Option<String>

Returns the URL

pub fn metadata_json(&self) -> String

Returns metadata as JSON

pub fn pixel_scale_x(&self) -> Option<f64>

Returns pixel scale X (degrees/pixel in lon direction)

pub fn pixel_scale_y(&self) -> Option<f64>

Returns pixel scale Y (degrees/pixel in lat direction, negative)

pub fn tiepoint_geo_x(&self) -> Option<f64>

Returns tiepoint geo X (top-left longitude)

pub fn tiepoint_geo_y(&self) -> Option<f64>

Returns tiepoint geo Y (top-left latitude)

pub async fn read_tile( &self, _level: usize, tile_x: u32, tile_y: u32, ) -> Result<Vec<u8>, JsValue>

Reads a tile and returns raw bytes

pub async fn read_tile_as_image_data( &self, level: usize, tile_x: u32, tile_y: u32, ) -> Result<ImageData, JsValue>

Reads a tile and converts to RGBA ImageData for canvas rendering

Trait Implementations

impl Default for WasmCogViewer

fn default() -> Self

Returns the “default value” for a type.

impl From<WasmCogViewer> for JsValue

fn from(value: WasmCogViewer) -> Self

Converts to this type from the input type.

impl FromWasmAbi for WasmCogViewer

type Abi = u32

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: u32) -> Self

Recover a Self from Self::Abi.

impl IntoWasmAbi for WasmCogViewer

type Abi = u32

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> u32

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl LongRefFromWasmAbi for WasmCogViewer

type Abi = u32

Same as RefFromWasmAbi::Abi

type Anchor = RcRef<WasmCogViewer>

Same as RefFromWasmAbi::Anchor

unsafe fn long_ref_from_abi(js: Self::Abi) -> Self::Anchor

Same as RefFromWasmAbi::ref_from_abi

impl OptionFromWasmAbi for WasmCogViewer

fn is_none(abi: &Self::Abi) -> bool

Tests whether the argument is a “none” instance. If so it will be deserialized as None, and otherwise it will be passed to FromWasmAbi.

impl OptionIntoWasmAbi for WasmCogViewer

fn none() -> Self::Abi

Returns an ABI instance indicating “none”, which JS will interpret as the None branch of this option.

impl RefFromWasmAbi for WasmCogViewer

type Abi = u32

The Wasm ABI type references to Self are recovered from.

type Anchor = RcRef<WasmCogViewer>

The type that holds the reference to Self for the duration of the invocation of the function that has an &Self parameter. This is required to ensure that the lifetimes don’t persist beyond one function call, and so that they remain anonymous.

unsafe fn ref_from_abi(js: Self::Abi) -> Self::Anchor

Recover a Self::Anchor from Self::Abi.

impl RefMutFromWasmAbi for WasmCogViewer

type Abi = u32

Same as RefFromWasmAbi::Abi

type Anchor = RcRefMut<WasmCogViewer>

Same as RefFromWasmAbi::Anchor

unsafe fn ref_mut_from_abi(js: Self::Abi) -> Self::Anchor

Same as RefFromWasmAbi::ref_from_abi

impl TryFromJsValue for WasmCogViewer

fn try_from_js_value(value: JsValue) -> Result<Self, JsValue>

Performs the conversion.

fn try_from_js_value_ref(value: &JsValue) -> Option<Self>

Performs the conversion.

impl VectorFromWasmAbi for WasmCogViewer

type Abi = <Box<[JsValue]> as FromWasmAbi>::Abi

unsafe fn vector_from_abi(js: Self::Abi) -> Box<[WasmCogViewer]>

impl VectorIntoWasmAbi for WasmCogViewer

type Abi = <Box<[JsValue]> as IntoWasmAbi>::Abi

fn vector_into_abi(vector: Box<[WasmCogViewer]>) -> Self::Abi

impl WasmDescribe for WasmCogViewer

fn describe()

impl WasmDescribeVector for WasmCogViewer

fn describe_vector()

impl SupportsConstructor for WasmCogViewer

impl SupportsInstanceProperty for WasmCogViewer

impl SupportsStaticProperty for WasmCogViewer