only grid_jpeg?

[j2l]

Hello @archmoj, Thank you for making a JS library to parse grib2 files. Using linux tool grib_ls, it seems that your all grib example files are grib_jpeg packingType.

Does grib2class also work for grid_simple packingType (wind on u and v axis, waves, ... on various dates and levels)?

I can't make it work for now in svelte but it might be my fault :smile:

[archmoj]

Simple and complex packing types should also work: https://github.com/archmoj/grib2class/blob/c0ca0a2dff7e8a218bd255f8c0468f7dee3abb10/grib2class.js#L1286-L1289

[j2l]

Thank you very much @archmoj

So, if it's not the packingType, I might not use it correctly to read values:

<script>
import GRIB2CLASS from 'grib2class'
async function readfile(e) {
  const file = await e.target.files[0];
  let gribouille = new GRIB2CLASS({
        numMembers: 1,
        log: false,
    });
    await gribouille.parse(file);
  console.log("gribouille: " + gribouille.getGrib2Section(0))
</script>

<input type="file" bind:files on:input={readfile}>

Any getGrib2Section returns 0 using example files as input (CMC_reg_TMP_TGL_2_ps10km_2019081112_P024.grib2 exactly).

Any idea?

[archmoj]

As far as I know CMC grib2 files are encoded in jpeg-2000 not simple packing. It should work if you provide the jpeg2000decoder function as illustrated in this example: https://github.com/archmoj/opengrib2/blob/master/opengrib2.js

[j2l]

I expected some info about the file, just to make sure it can read something. My other trials didn't throw something different. For example, a recent grib2 file from https://www.ncei.noaa.gov/data/global-forecast-system/access/grid-003-1.0-degree/analysis/202302/20230211/ is type grid_complex_spatial_differencing and shows same result: gribouille: 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

[archmoj]

What happens if you set log: true in your app? Could you possibly paste the log?

[j2l]

logger seems to be broken: Uncaught (in promise) TypeError: this is undefined < logger.js 38:12

[archmoj]

What would happen if you require the module instead of importing it? Similar to https://github.com/archmoj/opengrib2/blob/master/opengrib2.js

[j2l]

Thank you @archmoj Hmmm, getting "require is not defined" since it's Vite and Svelte (ESM). It's a well known wall because Svelte needs type=module (see https://isotropic.co/how-to-fix-referenceerror-require-is-not-defined-in-javascript/). Grib2class works without error as import though since you export it module.exports = function /* class */ GRIB2CLASS

I could try to redevelop it in Sveltekit to force server processing of require but I'm pretty sure it won't solve it.

[j2l]

yeah, another wall with SvelteKit, since it cannot pass it to the client:

Error: Data returned from `load` while rendering / is not serializable: Cannot stringify a function (data.grib2class)
    at Module.render_response (/node_modules/@sveltejs/kit/src/runtime/server/page/render.js:234:9)
    at async Module.render_page (/node_modules/@sveltejs/kit/src/runtime/server/page/index.js:303:10)
    at async resolve (/node_modules/@sveltejs/kit/src/runtime/server/respond.js:273:22)
    at async Module.respond (/node_modules/@sveltejs/kit/src/runtime/server/respond.js:175:22)
    at async file:///home/pm/Documents/github/sveltekit-grib/node_modules/@sveltejs/kit/src/exports/vite/dev/index.js:495:22

+page.server.js:

const grib2class = require("grib2class");

export const load = async ({locals}) => {
    return { 
        grib2class: grib2class
     };
};

It doesn't go further