Improve compression tests

Do not use any cmps. Instead check the difference in sizes between compressed
and decompressed pdfs.

DEVSIX-3391

Autoported commit.
Original commit hash: [8c64bac2d]

Author: ars18wrw

itext.tests/itext.kernel.tests/itext/kernel/pdf/PdfStampingTest.cs

@@ -1132,29 +1132,21 @@ public virtual void StampingTestWithTaggedStructure() {
 
         [NUnit.Framework.Test]
         public virtual void StampingTestWithFullCompression01() {
-            String outPdf = destinationFolder + "stampingTestWithFullCompression01.pdf";
-            String cmpPdf = sourceFolder + "cmp_stampingTestWithFullCompression01.pdf";
+            String compressedOutPdf = destinationFolder + "stampingTestWithFullCompression01Compressed.pdf";
+            String decompressedOutPdf = destinationFolder + "stampingTestWithFullCompression01Decompressed.pdf";
             PdfDocument pdfDoc = new PdfDocument(new PdfReader(sourceFolder + "fullCompressedDocument.pdf"), new PdfWriter
-                (outPdf));
+                (compressedOutPdf));
             pdfDoc.Close();
-            float result = new FileInfo(outPdf).Length;
-            float expected = new FileInfo(cmpPdf).Length;
-            float coef = Math.Abs((expected - result) / expected);
-            String compareRes = new CompareTool().CompareByContent(outPdf, cmpPdf, destinationFolder);
-            NUnit.Framework.Assert.IsTrue(coef < 0.01);
-            NUnit.Framework.Assert.IsNull(compareRes);
-        }
-
-        [NUnit.Framework.Test]
-        public virtual void StampingTestWithFullCompression02() {
-            PdfDocument pdfDoc = new PdfDocument(new PdfReader(sourceFolder + "fullCompressedDocument.pdf"), new PdfWriter
-                (destinationFolder + "stampingTestWithFullCompression02.pdf", new WriterProperties().SetFullCompressionMode
-                (false)));
+            float compressedLength = new FileInfo(compressedOutPdf).Length;
+            pdfDoc = new PdfDocument(new PdfReader(sourceFolder + "fullCompressedDocument.pdf"), new PdfWriter(decompressedOutPdf
+                , new WriterProperties().SetFullCompressionMode(false)));
             pdfDoc.Close();
-            float result = new FileInfo(destinationFolder + "stampingTestWithFullCompression02.pdf").Length;
-            float expected = new FileInfo(sourceFolder + "cmp_stampingTestWithFullCompression02.pdf").Length;
-            float coef = Math.Abs((expected - result) / expected);
-            NUnit.Framework.Assert.IsTrue(coef < 0.01);
+            float decompressedLength = new FileInfo(decompressedOutPdf).Length;
+            float coef = compressedLength / decompressedLength;
+            String compareRes = new CompareTool().CompareByContent(compressedOutPdf, decompressedOutPdf, destinationFolder
+                );
+            NUnit.Framework.Assert.IsTrue(coef < 0.7);
+            NUnit.Framework.Assert.IsNull(compareRes);
         }
 
         [NUnit.Framework.Test]

itext.tests/itext.kernel.tests/resources/itext/kernel/pdf/PdfStampingTest/cmp_stampingTestWithFullCompression01.pdf

@@ -1 +1 @@
-d8ecda465d2a1a94c54f3d51be94b46addff6ba7
+8c64bac2d21ffb918af4f0d40f9864f787bf5e30