Import and export PDF annotations from Instant JSON in Flutter
Nutrient Flutter SDK uses the Instant JSON format to import and export annotations. This guide shows how to import and export annotations with Instant JSON.
Details
Instant JSON stores annotations in a modern format while preserving the properties PDF annotations need. The format is documented and supports long-term storage.
Instant JSON enables you to store PDF changes, such as annotations, in a separate JSON file. You transfer the PDF document once and then apply changes as an overlay to the existing PDF. This approach reduces bandwidth because you transfer the JSON instead of the complete PDF.
Conceptually, Instant JSON defines a list of skippedPdfObjectIds. These values point to the PDF’s internal object IDs for annotations. When you mark an object ID as skipped, the SDK no longer loads it from the original PDF. Instead, you can define it inside the annotations array with the same pdfObjectId. In this case, the PDF viewer displays the new annotation, which signals an update to the original annotation. If you mark an object ID as skipped but the annotations array doesn’t contain an annotation with the same pdfObjectId, the SDK interprets it as a deleted annotation. The SDK interprets an annotation inside the annotations array without the pdfObjectId property as a new annotation.
All annotations in the annotations array have a unique id field. For annotations updated from the original PDF, this field uses the stringified pdfObjectId. Newly created annotations get a newly generated ULID(opens in a new tab).
An “empty” Instant JSON contains neither skippedPdfObjectIds nor annotations, which means the original PDF remains unchanged. The SDK still shows all annotations from the initial PDF.
Import Instant JSON
Add an existing Instant JSON payload to a document by calling applyInstantJson(annotationsJSON):
// Create an Instant JSON payload.final annotationsJson = ''' { "annotations": [{ "bbox": [18.4609375, 582.3333740234375, 431.6640625, 426.00003051757812], "blendMode": "normal", "createdAt": "2019-11-15T15:36:25Z", "creatorName": "PSPDFKit", "isDrawnNaturally": false, "lineWidth": 10, "lines": { "intensities": [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], "points": [[[271.6171875, 598], [266.93331909179688, 595.16668701171875], [259.71206665039062, 591.5833740234375], [255.27398681640625, 590.16668701171875], [248.65992736816406, 588.75], [244.59376525878906, 588.0030517578125], [239.75138854980469, 587.3333740234375], [234.60507202148438, 587.3333740234375], [229.98934936523438, 587.3333740234375], [225.3984375, 588.5908203125], [218.64601135253906, 588.75], [212.66595458984375, 588.75], [206.78047180175781, 590.16668701171875], [190.50941467285156, 591.5833740234375], [179.1796875, 593.75], [167.80718994140625, 595.16668701171875], [158.66848754882812, 596.5833740234375], [150.61857604980469, 598], [144.00840759277344, 600.125], [139.43266296386719, 600.125], [135.82032775878906, 601.54168701171875], [130.93865966796875, 604.41668701171875], [125.97789764404297, 607.9583740234375], [120.16405487060547, 609.6793212890625], [114.53083038330078, 612.2083740234375], [109.08804321289062, 614.375], [104.01295471191406, 616.29022216796875], [98.109375, 619.43707275390625], [92.337196350097656, 622.16668701171875], [87.625740051269531, 625.04168701171875], [82.543983459472656, 628.5833740234375], [77.507820129394531, 631.41668701171875], [71.68023681640625, 636.41668701171875], [68.25, 641.36651611328125], [63.281246185302734, 644.66424560546875], [58.289066314697266, 650.6976318359375], [54.0234375, 658.99774169921875], [49.0546875, 669.7379150390625], [42.656242370605469, 681.2083740234375], [37.6875, 694.83612060546875], [32.695316314697266, 707.46807861328125], [29.859375, 717.4583740234375], [28.429689407348633, 730.241943359375], [24.867185592651367, 742.06866455078125], [24.867185592651367, 753.7083740234375], [23.4609375, 768.94134521484375], [23.4609375, 782.875], [23.4609375, 799.98004150390625], [23.4609375, 814.16668701171875], [24.867185592651367, 828.375], [27, 841.2083740234375], [29.859375, 854], [32.695316314697266, 867.92138671875], [36.257816314697266, 880.78863525390625], [41.226566314697266, 893.8333740234375], [42.656242370605469, 904.97161865234375], [44.085941314697266, 913.21966552734375], [45.185382843017578, 919.41668701171875], [48.017143249511719, 928.0272216796875], [51.890621185302734, 937.18316650390625], [56.882816314697266, 946.41668701171875], [61.938720703125, 952.8333740234375], [64.687507629394531, 957.05609130859375], [70.581169128417969, 962.0833740234375], [78.143966674804688, 968.4583740234375], [86.742179870605469, 973.4583740234375], [96.703125, 979.875], [109.5, 984.125], [124.87102508544922, 989.0833740234375], [137.95753479003906, 992.66668701171875], [149.32032775878906, 995.5], [163.54685974121094, 999.04168701171875], [184.17189025878906, 1000.4583740234375], [209.76560974121094, 1001.9166870117188], [231.79685974121094, 1003.3333740234375], [250.99217224121094, 1003.3333740234375], [265.053955078125, 1003.3333740234375], [276.60940551757812, 1003.3333740234375], [287.2734375, 1001.9166870117188], [301.83041381835938, 1000.2388916015625], [317.83590698242188, 995.5], [333.4921875, 992.66668701171875], [345.98687744140625, 984.57415771484375], [355.52838134765625, 976.28839111328125], [366.91409301757812, 965.625], [384.67971801757812, 952.8333740234375], [401.74224853515625, 941.4583740234375], [414.5625, 932.2083740234375], [425.454345703125, 924.84600830078125], [432.32809448242188, 915.875], [436.59375, 901.6387939453125], [441.58590698242188, 881], [442.99221801757812, 854], [445.125, 830.54168701171875], [445.125, 807.79168701171875], [442.99221801757812, 788.7923583984375], [440.15625, 771.5], [435.16409301757812, 752.2916259765625], [430.19534301757812, 736.66668701171875], [427.35934448242188, 724.387451171875], [424.5, 715.0751953125], [420.96090698242188, 708.2083740234375], [415.96810913085938, 698.25], [410.59469604492188, 690.4583740234375], [406.734375, 682.9306640625], [403.17190551757812, 677.268798828125], [400.33590698242188, 671.87744140625], [395.66424560546875, 668.41668701171875], [389.95599365234375, 662.67138671875], [381.23092651367188, 657], [373.3125, 650.625], [366.91409301757812, 645.625], [360.19537353515625, 641.375], [354.17913818359375, 637.8333740234375], [349.00265502929688, 634.9583740234375], [345.44509887695312, 631.41668701171875], [339.6290283203125, 628.5833740234375], [334.68048095703125, 625.04168701171875], [330.84097290039062, 623.5833740234375], [325.87319946289062, 622.16668701171875], [319.62060546875, 620.75], [315.2069091796875, 618.625], [309.99786376953125, 618.6029052734375], [304.51095581054688, 617.2083740234375], [300.08163452148438, 617.2083740234375], [297.23440551757812, 616.544189453125], [292.9212646484375, 615.7916259765625], [287.88607788085938, 615.7916259765625], [283.19888305664062, 615.7916259765625], [277.85714721679688, 615.7916259765625], [273.72171020507812, 615.043701171875], [268.078125, 614.58349609375], [264.75930786132812, 615.7916259765625], [260.88003540039062, 615.7916259765625], [256.7109375, 615.7916259765625], [252.39967346191406, 617.2083740234375], [247.453125, 622.875], [243.87890625, 623.5833740234375], [239.98826599121094, 625.04168701171875]]] }, "name": "ed9b4f2f-8178-4b69-9c50-bb59f820e10e", "opacity": 1, "pageIndex": 0, "strokeColor": "#2196F3", "type": "pspdfkit/ink", "updatedAt": "2019-11-15T15:36:25Z", "v": 1 }], "format": "https://pspdfkit.com/instant-json/v1", "pdfId": { "changing": "3llO8Q1c9h7lim6xrsd3BQ==", "permanent": "2ShIBg/xQBK0uIs748b8Ng==" } }''';
await controller.document.applyInstantJson(annotationsJson);Export Instant JSON
Export a document’s current annotations as an Instant JSON payload by calling exportInstantJson():
final annotationsJSON = await controller.document.exportInstantJson();print(annotationsJSON); // Will print all the unsaved annotations in the document.Only unsaved annotations will be exported.