Stirling-PDF/src/main/java/stirling/software/SPDF/controller/api/ToSinglePageController.java

package stirling.software.SPDF.controller.api;

import java.awt.geom.AffineTransform;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.common.PDStream;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;



import io.swagger.v3.oas.annotations.Operation;
import io.swagger.v3.oas.annotations.Parameter;
import io.swagger.v3.oas.annotations.tags.Tag;
import stirling.software.SPDF.utils.WebResponseUtils;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.multipdf.LayerUtility;
@RestController
@Tag(name = "General", description = "General APIs")
public class ToSinglePageController {

    private static final Logger logger = LoggerFactory.getLogger(ToSinglePageController.class);

   
    @PostMapping(consumes = "multipart/form-data", value = "/pdf-to-single-page")
    @Operation(
        summary = "Convert a multi-page PDF into a single long page PDF",
        description = "This endpoint converts a multi-page PDF document into a single paged PDF document. The width of the single page will be same as the input's width, but the height will be the sum of all the pages' heights. Input:PDF Output:PDF Type:SISO"
    )
    public ResponseEntity<byte[]> pdfToSinglePage(
        @RequestPart(required = true, value = "fileInput")
        @Parameter(description = "The input multi-page PDF file to be converted into a single page", required = true)
            MultipartFile file) throws IOException {

    	// Load the source document
    	PDDocument sourceDocument = PDDocument.load(file.getInputStream());

    	// Calculate total height and max width
    	float totalHeight = 0;
    	float maxWidth = 0;
    	for (PDPage page : sourceDocument.getPages()) {
    	    PDRectangle pageSize = page.getMediaBox();
    	    totalHeight += pageSize.getHeight();
    	    maxWidth = Math.max(maxWidth, pageSize.getWidth());
    	}

    	// Create new document and page with calculated dimensions
    	PDDocument newDocument = new PDDocument();
    	PDPage newPage = new PDPage(new PDRectangle(maxWidth, totalHeight));
    	newDocument.addPage(newPage);

    	// Initialize the content stream of the new page
    	PDPageContentStream contentStream = new PDPageContentStream(newDocument, newPage);
    	contentStream.close();
    	
    	LayerUtility layerUtility = new LayerUtility(newDocument);
    	float yOffset = totalHeight;

    	// For each page, copy its content to the new page at the correct offset
    	for (PDPage page : sourceDocument.getPages()) {
    	    PDFormXObject form = layerUtility.importPageAsForm(sourceDocument, sourceDocument.getPages().indexOf(page));
    	    AffineTransform af = AffineTransform.getTranslateInstance(0, yOffset - page.getMediaBox().getHeight());
    	    layerUtility.wrapInSaveRestore(newPage);
    	    String defaultLayerName = "Layer" + sourceDocument.getPages().indexOf(page);
    	    layerUtility.appendFormAsLayer(newPage, form, af, defaultLayerName);
    	    yOffset -= page.getMediaBox().getHeight();
    	}

    	ByteArrayOutputStream baos = new ByteArrayOutputStream();
    	newDocument.save(baos);
    	newDocument.close();
    	sourceDocument.close();

    	byte[] result = baos.toByteArray();
    	return WebResponseUtils.bytesToWebResponse(result, file.getOriginalFilename().replaceFirst("[.][^.]+$", "") + "_singlePage.pdf");



       
    }
}