Add debugBorder and pageThreshhold options to Processor constru…

…ctor

Add 1-pixel default fudge factor to pyramid page selection

README.md

@@ -30,9 +30,11 @@ const processor = new IIIF.Processor(url, streamResolver, opts);
     * `height` (integer) - the maximum pixel height of the returned image
     * `area` (integer) - the maximum total number of pixels in the returned image
   * `includeMetadata` (boolean) – if `true`, all metadata from the source image will be copied to the result
+  * `debugBorder` (boolean) – if `true`, add a 1px red border to every generated image (for tile debugging)
   * `density` (integer) – the pixel density to be included in the result image in pixels per inch
     * This has no effect whatsoever on the size of the image that gets returned; it's simply for convenience when using
       the resulting image in software that calculates a default print size based on the height, width, and density
+  * `pageThreshold` (integer) – the fudge factor (in number of pixels) to mitigate rounding errors in pyramid page selection (default: `1`)
   * `pathPrefix` (string) – the template used to extract the IIIF version and API parameters from the URL path (default: `/iiif/{{version}}/`) ([see below](#path-prefix))
   * `version` (number) – the major version (`2` or `3`) of the IIIF Image API to use (default: inferred from `/iiif/{version}/`)
 

examples/tiny-iiif/iiif.js

@@ -1,5 +1,6 @@
 import { App } from '@tinyhttp/app';
-import { Processor } from 'iiif-processor';
+import iiif from 'iiif-processor';
+const { Processor } = iiif;
 import fs from 'fs';
 import path from 'path';
 import { iiifImagePath, iiifpathPrefix, fileTemplate } from './config.js';
@@ -21,7 +22,7 @@ function createRouter(version) {
 
     try {
       const iiifUrl = `${req.protocol}://${req.get("host")}${req.path}`;
-      const iiifProcessor = new Processor(iiifUrl, streamImageFromFile, { pathPrefix: iiifpathPrefix });
+      const iiifProcessor = new Processor(iiifUrl, streamImageFromFile, { pathPrefix: iiifpathPrefix, debugBorder: !!process.env.DEBUG_IIIF_BORDER });
       const result = await iiifProcessor.execute();
       return res
         .set("Content-Type", result.contentType)

src/processor.js

@@ -1,4 +1,5 @@
 const debug = require('debug')('iiif-processor:main');
+const debugv = require('debug')('verbose:iiif-processor');
 const mime = require('mime-types');
 const path = require('path');
 const sharp = require('sharp');
@@ -51,6 +52,8 @@ class Processor {
     this.includeMetadata = !!opts.includeMetadata;
     this.density = opts.density;
     this.baseUrl = opts.prefix;
+    this.debugBorder = !!opts.debugBorder;
+    this.pageThreshold = opts.pageThreshold;
     this.sharpOptions = { ...opts.sharpOptions };
     this.version = opts.iiifVersion;
     this.request = opts.request;
@@ -147,8 +150,9 @@ class Processor {
   }
 
   operations (dim) {
-    const { sharpOptions: sharp, max } = this;
-    return new Operations(this.version, dim, { sharp, max })
+    const { sharpOptions: sharp, max, pageThreshold } = this;
+    debug('pageThreshold: %d', pageThreshold);
+    return new Operations(this.version, dim, { sharp, max, pageThreshold })
       .region(this.region)
       .size(this.size)
       .rotation(this.rotation)
@@ -157,14 +161,39 @@ class Processor {
       .withMetadata(this.includeMetadata);
   }
 
+  async applyBorder (transformed) {
+    const buf = await transformed.toBuffer();
+    const borderPipe = sharp(buf, { limitInputPixels: false })
+    const { width, height } = await borderPipe.metadata();
+    const background = { r: 255, g: 0, b: 0, alpha: 1 };
+
+    // Create small images for each border “strip”
+    const topBorder = { create: { width, height: 1, channels: 4, background } };
+    const bottomBorder = { create: { width, height: 1, channels: 4, background } };
+    const leftBorder = { create: { width: 1, height, channels: 4, background } };
+    const rightBorder = { create: { width: 1, height, channels: 4, background } };
+
+    return borderPipe.composite([
+      { input: topBorder, left: 0, top: 0 },
+      { input: bottomBorder, left: 0, top: height - 1 },
+      { input: leftBorder, left: 0, top: 0 },
+      { input: rightBorder, left: width - 1, top: 0 }
+    ]);
+  }
+
   async iiifImage () {
+    debugv('Request %s', this.request);
     const dim = await this.dimensions();
     const operations = this.operations(dim);
+    debugv('Operations: %j', operations);
     const pipeline = await operations.pipeline();
 
     const result = await this.withStream({ id: this.id, baseUrl: this.baseUrl }, async (stream) => {
       debug('piping stream to pipeline');
-      const transformed = await stream.pipe(pipeline);
+      let transformed = await stream.pipe(pipeline);
+      if (this.debugBorder) {
+        transformed = await this.applyBorder(transformed);
+      }
       debug('converting to buffer');
       return await transformed.toBuffer();
     });

src/transform.js

@@ -9,16 +9,18 @@ const ExtractAttributes = [
   'heightPre'
 ];
 
+const DEFAULT_PAGE_THRESHOLD = 1;
 const SCALE_PRECISION = 10000000;
 
 class Operations {
   #pages;
   #pipeline;
 
   constructor (version, dims, opts) {
-    const { sharp, ...rest } = opts;
+    const { sharp, pageThreshold, ...rest } = opts;
     const Implementation = IIIFVersions[version];
     this.calculator = new Implementation.Calculator(dims[0], rest);
+    this.pageThreshold = typeof pageThreshold === 'number' ? pageThreshold : DEFAULT_PAGE_THRESHOLD;
 
     this.#pages = dims
       .map((dim, page) => {
@@ -119,8 +121,8 @@ class Operations {
     const { fullSize } = this.info();
     const { page } = this.#pages.find((_candidate, index) => {
       const next = this.#pages[index + 1];
-      debug('comparing candidate %j to target %j', next, fullSize);
-      return !next || (next.width < fullSize.width && next.height < fullSize.height);
+      debug('comparing candidate %j to target %j with a %d-pixel buffer', next, fullSize, this.pageThreshold);
+      return !next || (next.width + this.pageThreshold < fullSize.width && next.height + this.pageThreshold < fullSize.height);
     });
 
     const resolution = this.#pages[page];

tests/v2/integration.test.js

@@ -88,6 +88,17 @@ describe('size', () => {
     pipeline = await subject.operations(await subject.dimensions()).pipeline();
     assert.strictEqual(pipeline.options.input.page, 1);
   });
+
+  it('should respect the pixel page buffer', async () => {
+    let pipeline;
+    subject = new Processor(`${base}/full/312,165/0/default.png`, streamResolver);
+    pipeline = await subject.operations(await subject.dimensions()).pipeline();
+    assert.strictEqual(pipeline.options.input.page, 1);
+
+    subject = new Processor(`${base}/full/312,165/0/default.png`, streamResolver, { pageThreshold: 0 });
+    pipeline = await subject.operations(await subject.dimensions()).pipeline();
+    assert.strictEqual(pipeline.options.input.page, 0);
+  });
 });
 
 describe('rotation', () => {
@@ -146,3 +157,21 @@ describe('Two-argument streamResolver', () => {
     assert.strictEqual(size.format, 'png');
   });
 });
+
+describe('Debug border', () => {
+  it('should produce an image without a border by default', async () => {
+    subject = new Processor(`${base}/full/full/0/default.png`, streamResolver);
+    const result = await subject.execute();
+    const image = await Sharp(result.body).removeAlpha().raw().toBuffer();
+    const pixel = image.readUInt32LE(0);
+    assert.strictEqual(pixel, 0xffffffff);
+  });
+
+  it('should add a border when `debugBorder` is specified', async () => {
+    subject = new Processor(`${base}/full/full/0/default.png`, streamResolver, { debugBorder: true });
+    const result = await subject.execute();
+    const image = await Sharp(result.body).removeAlpha().raw().toBuffer();
+    const pixel = image.readUInt32LE(0);
+    assert.strictEqual(pixel, 0xff0000ff);
+  });
+});

tests/v3/integration.test.js

@@ -88,6 +88,17 @@ describe('size', () => {
     pipeline = await subject.operations(await subject.dimensions()).pipeline();
     assert.strictEqual(pipeline.options.input.page, 1);
   });
+
+  it('should respect the pixel page buffer', async () => {
+    let pipeline;
+    subject = new Processor(`${base}/full/312,165/0/default.png`, streamResolver);
+    pipeline = await subject.operations(await subject.dimensions()).pipeline();
+    assert.strictEqual(pipeline.options.input.page, 1);
+
+    subject = new Processor(`${base}/full/312,165/0/default.png`, streamResolver, { pageThreshold: 0 });
+    pipeline = await subject.operations(await subject.dimensions()).pipeline();
+    assert.strictEqual(pipeline.options.input.page, 0);
+  });
 });
 
 describe('rotation', () => {
@@ -144,3 +155,21 @@ describe('Two-argument streamResolver', () => {
     assert.strictEqual(size.format, 'png');
   });
 });
+
+describe('Debug border', () => {
+  it('should produce an image without a border by default', async () => {
+    subject = new Processor(`${base}/full/max/0/default.png`, streamResolver);
+    const result = await subject.execute();
+    const image = await Sharp(result.body).removeAlpha().raw().toBuffer();
+    const pixel = image.readUInt32LE(0);
+    assert.strictEqual(pixel, 0xffffffff);
+  });
+
+  it('should add a border when `debugBorder` is specified', async () => {
+    subject = new Processor(`${base}/full/max/0/default.png`, streamResolver, { debugBorder: true });
+    const result = await subject.execute();
+    const image = await Sharp(result.body).removeAlpha().raw().toBuffer();
+    const pixel = image.readUInt32LE(0);
+    assert.strictEqual(pixel, 0xff0000ff);
+  });
+});