Add HTTP reader based example

Cargo.toml

@@ -19,3 +19,5 @@ tiff = { git = "https://github.com/image-rs/image-tiff" }
 
 [dev-dependencies]
 image = "0.24.5"
+http-range-client = "0.7.0"
+env_logger = "0.10.0"

README.md

@@ -47,4 +47,6 @@ cargo run --example pixel data/tiff/N265E425.tif 2550 3050
 cargo run --example crop data/tiff/N265E425.tif 100x100+2500+3000 dtm.png
 
 cargo run --example img2ascii data/tiff/sat.tif
+
+cargo run --example http_dtm
 ```

examples/http_dtm.rs

@@ -0,0 +1,61 @@
+use georaster::geotiff::{GeoTiffReader, RasterValue};
+use http_range_client::HttpReader;
+
+fn main() {
+    env_logger::init();
+    let mut img_reader = HttpReader::new("https://data.sourcepole.com/srtm_1km_3857.tif");
+    // File size: 244M
+    // gdalinfo:
+    // Driver: GTiff/GeoTIFF
+    // Files: srtm_1km_3857.tif
+    // Size is 41999, 17610
+    // Coordinate System is:
+    //     ID["EPSG",3857]]
+    // Data axis to CRS axis mapping: 1,2
+    // Origin = (-20037506.487966008484364,8401593.447238374501467)
+    // Pixel Size = (954.174162299386694,-954.196881813704067)
+    // Metadata:
+    //   AREA_OR_POINT=Area
+    // Image Structure Metadata:
+    //   COMPRESSION=DEFLATE
+    //   INTERLEAVE=BAND
+    // Corner Coordinates:
+    // Upper Left  (-20037506.488, 8401593.447) (179d59'59.94"W, 60d 0'30.00"N)
+    // Lower Left  (-20037506.488,-8401813.642) (179d59'59.94"W, 60d 0'33.56"S)
+    // Upper Right (20036854.154, 8401593.447) (179d59'38.84"E, 60d 0'30.00"N)
+    // Lower Right (20036854.154,-8401813.642) (179d59'38.84"E, 60d 0'33.56"S)
+    // Center      (    -326.167,    -110.097) (  0d 0'10.55"W,  0d 0' 3.56"S)
+    // Band 1 Block=256x256 Type=Int32, ColorInterp=Gray
+    //   NoData Value=-9999
+    //   Overviews: 5250x2202, 657x276, 83x35
+
+    // img_reader.set_min_req_size(1_048_576); // 1MB 6 requests, 6'291'456 B
+    // img_reader.set_min_req_size(524288); // 512KB 7 requests, 3'670'016 B
+    img_reader.set_min_req_size(262144); // 256KB 7 requests, 1'835'008 B
+
+    let mut tiff = GeoTiffReader::open(img_reader).expect("Cannot create decoder");
+
+    let img = tiff.images().get(0).expect("Image info");
+    assert_eq!(img.dimensions, Some((41999, 17610)));
+    assert_eq!(img.colortype, Some(tiff::ColorType::Gray(32)));
+    assert_eq!(tiff.origin(), Some([-20037506.48796601, 8401593.447238375]));
+    assert_eq!(
+        tiff.pixel_size(),
+        Some([954.1741622993867, -954.1968818137041])
+    );
+    assert_eq!(
+        tiff.geo_params,
+        Some("WGS 84 / Pseudo-Mercator|WGS 84|".to_string())
+    );
+
+    tiff.seek_to_image(0).unwrap();
+    assert_eq!(tiff.read_pixel(20000, 8000), RasterValue::I32(372));
+
+    // Read medium overview
+    tiff.seek_to_image(1).unwrap();
+    let max_height = tiff
+        .pixels(0, 0, 657, 276)
+        .map(|(_x, _y, h)| if let RasterValue::I32(v) = h { v } else { 0 })
+        .max();
+    assert_eq!(max_height, Some(3405));
+}