Fetch binary chunk and draw on canvas

web/src/harmonie/draw/bounds.ts

@@ -0,0 +1,32 @@
+import { GribMessage } from '../../interfaces/interfaces'
+import { CropBounds } from './drawGrib'
+
+export function extractFromBounds(
+    grib: GribMessage,
+    source: Uint8Array,
+    cropBounds: CropBounds,
+): Uint8Array {
+    const { grid, bitsPerDataPoint } = grib
+    const bytesPerPoint = bitsPerDataPoint / 8
+    const { x, y, width, height } = cropBounds
+
+    if (
+        x < 0
+        || y < 0
+        || x + width > grid.cols-1
+        || y + height > grid.rows-1
+    ) {
+        throw new Error('Extract bbox out of grid bounds')
+    }
+
+    const output = new Uint8Array(width*height*bytesPerPoint)
+    for (let row=y, i=0; row < y+height; row++) {
+        const inputOffset = (row*grid.cols + x)*bytesPerPoint
+        const readBytes = width*bytesPerPoint
+        const inputBuffer = source.slice(inputOffset, inputOffset+readBytes)
+        output.set(inputBuffer, i)
+        i += readBytes
+    }
+
+    return output
+}