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Implemented RPC Coefficient handling #441

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Implemented RPC Coefficient handling #441

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33 changes: 33 additions & 0 deletions src/geotiff.js
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Original file line number Diff line number Diff line change
Expand Up @@ -422,13 +422,46 @@ class GeoTIFF extends GeoTIFFBase {
offset + offsetSize + (entrySize * numDirEntries),
);

// Parse RPC coefficients if available
if (fileDirectory.RPCCoefficient && fileDirectory.RPCCoefficient.length === 92) {
fileDirectory.RPCCoefficient = this.parseRPCCoefficients(fileDirectory.RPCCoefficient);
} else if (fileDirectory.RPCCoefficient) {
console.warn('Invalid RPCCoefficient length');
}

return new ImageFileDirectory(
fileDirectory,
geoKeyDirectory,
nextIFDByteOffset,
);
}

parseRPCCoefficients(rpcArray) {
if (rpcArray.length !== 92) {
console.warn(`Invalid RPCCoefficient length. Expected 92, got ${rpcArray.length}`);
return null;
}

return {
ERR_BIAS: rpcArray[0],
ERR_RAND: rpcArray[1],
LINE_OFF: rpcArray[2],
SAMP_OFF: rpcArray[3],
LAT_OFF: rpcArray[4],
LONG_OFF: rpcArray[5],
HEIGHT_OFF: rpcArray[6],
LINE_SCALE: rpcArray[7],
SAMP_SCALE: rpcArray[8],
LAT_SCALE: rpcArray[9],
LONG_SCALE: rpcArray[10],
HEIGHT_SCALE: rpcArray[11],
LINE_NUM_COEFF: rpcArray.slice(12, 32),
LINE_DEN_COEFF: rpcArray.slice(32, 52),
SAMP_NUM_COEFF: rpcArray.slice(52, 72),
SAMP_DEN_COEFF: rpcArray.slice(72, 92),
};
}

async requestIFD(index) {
// see if we already have that IFD index requested.
if (this.ifdRequests[index]) {
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3 changes: 3 additions & 0 deletions src/globals.js
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,7 @@ export const fieldTagNames = {
0x87AF: 'GeoKeyDirectory',
0x87B0: 'GeoDoubleParams',
0x87B1: 'GeoAsciiParams',
0xC69C: 'RPCCoefficient',

// LERC
0xC5F2: 'LercParameters',
Expand Down Expand Up @@ -171,6 +172,7 @@ export const fieldTagTypes = {
34736: 'DOUBLE',
34737: 'ASCII',
42113: 'ASCII',
50844: 'DOUBLE',
};

export const arrayFields = [
Expand All @@ -183,6 +185,7 @@ export const arrayFields = [
fieldTags.TileByteCounts,
fieldTags.TileOffsets,
fieldTags.SubIFDs,
fieldTags.RPCCoefficient,
];

export const fieldTypeNames = {
Expand Down