Initial commit: PaperScan — lokale Android documentscanner voor Paperless-ngx

Native Kotlin/Compose app met CameraX + OpenCV randdetectie/perspectiefcorrectie, multi-page PDF-export, en Paperless-ngx upload (of Android deelmenu). Alles lokaal. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-12 22:43:09 +02:00
commit 037550afa9
37 changed files with 2051 additions and 0 deletions
--- a/app/src/main/java/eu/geyskens/pdfscan/pdf/PdfBuilder.kt
+++ b/app/src/main/java/eu/geyskens/pdfscan/pdf/PdfBuilder.kt
@@ -0,0 +1,60 @@
+package eu.geyskens.pdfscan.pdf
+
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.Paint
+import android.graphics.Rect
+import android.graphics.pdf.PdfDocument
+import java.io.File
+import java.io.FileOutputStream
+
+/** How each PDF page is sized relative to its scanned image. */
+enum class PageSizeMode { A4, ORIGINAL }
+
+object PdfBuilder {
+
+    // A4 in PostScript points (1/72"): 210 x 297 mm.
+    private const val A4_WIDTH_PT = 595
+    private const val A4_HEIGHT_PT = 842
+
+    /**
+     * Writes [pages] into a single multi-page PDF at [output].
+     * With [PageSizeMode.A4] each image is centered and scaled to fit an A4 page
+     * (portrait or landscape chosen per image); with ORIGINAL the page matches the image.
+     */
+    fun build(pages: List<Bitmap>, output: File, mode: PageSizeMode = PageSizeMode.A4) {
+        require(pages.isNotEmpty()) { "Cannot build a PDF with no pages." }
+        val doc = PdfDocument()
+        val paint = Paint(Paint.FILTER_BITMAP_FLAG or Paint.ANTI_ALIAS_FLAG)
+        try {
+            pages.forEachIndexed { index, bitmap ->
+                val (pageW, pageH) = when (mode) {
+                    PageSizeMode.ORIGINAL -> bitmap.width to bitmap.height
+                    PageSizeMode.A4 ->
+                        if (bitmap.width >= bitmap.height) A4_HEIGHT_PT to A4_WIDTH_PT // landscape
+                        else A4_WIDTH_PT to A4_HEIGHT_PT
+                }
+                val info = PdfDocument.PageInfo.Builder(pageW, pageH, index + 1).create()
+                val page = doc.startPage(info)
+                val canvas = page.canvas
+                canvas.drawColor(Color.WHITE)
+                canvas.drawBitmap(bitmap, null, fitRect(bitmap, pageW, pageH), paint)
+                doc.finishPage(page)
+            }
+            FileOutputStream(output).use { doc.writeTo(it) }
+        } finally {
+            doc.close()
+        }
+    }
+
+    /** Largest centered rect inside the page that preserves the bitmap's aspect ratio. */
+    private fun fitRect(bitmap: Bitmap, pageW: Int, pageH: Int): Rect {
+        val scale = minOf(pageW.toFloat() / bitmap.width, pageH.toFloat() / bitmap.height)
+        val w = (bitmap.width * scale).toInt()
+        val h = (bitmap.height * scale).toInt()
+        val left = (pageW - w) / 2
+        val top = (pageH - h) / 2
+        return Rect(left, top, left + w, top + h)
+    }
+}