Searching watermarks Leave feedback
GroupDocs.Watermark API allows you to search the possible watermarks placed in any document. You can also search the watermarks that are added using some third-party tool. The API provides search method to search watermarks in a whole document or in any part of the document. Following code snippet shows how to find and get all possible watermarks in a document.
// Create an instance of Watermarker
const watermarker = new groupdocsWatermark.Watermarker('sample.pdf');
const watermarks = watermarker.search();
// Iterate through found watermarks
for (const watermark of watermarks.getInnerList().toArray()) {
console.log(watermark.getText());
console.log(watermark.getRotateAngle());
console.log(watermark.getX());
console.log(watermark.getY());
console.log(watermark.getWidth());
console.log(watermark.getHeight())
}
You can use search criteria to find objects with some specific parameters.
Following code snippet shows how to search for the watermarks that meet a particular text criterion
// Create watermarker
const watermarker = new groupdocsWatermark.Watermarker('sample.pdf');
// Define search criteria
const searchCriteria = new groupdocsWatermark.TextSearchCriteria("test", false);
// Search for watermarks
const watermarks = watermarker.search(searchCriteria);
console.log(`Found ${watermarks.getCount()} possible watermark(s).`);
Sometimes a document can contain image watermarks, and it’s necessary to find them using sample picture. For example, you may want to find all possible image watermarks that are similar to a company logo. Following sample code searches for image watermarks that resemble with a particular image using.
// Create watermarker
const watermarker = new groupdocsWatermark.Watermarker('sample.pdf');
// Initialize search criteria with the image
const imageSearchCriteria = new groupdocsWatermark.ImageDctHashSearchCriteria('logo.png');
// Set maximum allowed difference between images
imageSearchCriteria.setMaxDifference(0.9);
// Search for possible watermarks matching the criteria
const possibleWatermarks = watermarker.search(imageSearchCriteria);
console.log(`Found ${possibleWatermarks.getCount()} possible watermark(s).`);
MaxDifference property is used to set maximum allowed difference between sample image and possible watermark. The value should be between 0 and 1. The value 0 means that only identical images will be found. Using of ImageDctHashSearchCriteria is the most efficient way to find image watermark by a sample. This criterion uses DCT (Discrete Cosine Transform) based perceptual hash for image similarity comparison. But there are other image search criteria that are based on other algorithms:
GroupDocs.Watermark API also allows you to search watermarks by a combination of different search criteria. Following sample code shows how to search watermark with the combination of different search criteria.
// Create watermarker
const watermarker = new groupdocsWatermark.Watermarker('sample.pdf');
// Define image search criteria
const imageSearchCriteria = new groupdocsWatermark.ImageDctHashSearchCriteria('logo.png');
imageSearchCriteria.setMaxDifference(0.9);
// Define text search criteria
const textSearchCriteria = new groupdocsWatermark.TextSearchCriteria("Company Name");
// Define rotate angle search criteria
const rotateAngleSearchCriteria = new groupdocsWatermark.RotateAngleSearchCriteria(30, 60);
// Combine search criteria
const combinedSearchCriteria = imageSearchCriteria.or(textSearchCriteria).and(rotateAngleSearchCriteria);
// Search for possible watermarks
const possibleWatermarks = watermarker.search(combinedSearchCriteria);
// Output the results
console.log(`Found ${possibleWatermarks.getCount()} possible watermark(s).`);
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