Creator optimize drawing blocks (#136)

* Merge blocks and draw to page once
* Adapt stream compression test case
* Preserve original behavior of the raw stream compression test case

creator/creator.go

@@ -20,6 +20,8 @@ import (
 // content onto imported PDF pages, etc.
 type Creator struct {
 	pages      []*model.PdfPage
+	pageBlocks map[*model.PdfPage]*Block
+
 	activePage *model.PdfPage
 
 	pagesize PageSize
@@ -116,6 +118,7 @@ type margins struct {
 func New() *Creator {
 	c := &Creator{}
 	c.pages = []*model.PdfPage{}
+	c.pageBlocks = map[*model.PdfPage]*Block{}
 	c.SetPageSize(PageSizeLetter)
 
 	m := 0.1 * c.pageWidth
@@ -513,6 +516,15 @@ func (c *Creator) finalize() error {
 				return err
 			}
 		}
+
+		// Draw blocks to pages.
+		block, ok := c.pageBlocks[page]
+		if !ok {
+			return errors.New("could not find page block")
+		}
+		if err := block.drawToPage(page); err != nil {
+			return err
+		}
 	}
 
 	c.finalized = true
@@ -559,15 +571,21 @@ func (c *Creator) Draw(d Drawable) error {
 		return err
 	}
 
-	for idx, blk := range blocks {
+	for idx, block := range blocks {
 		if idx > 0 {
 			c.NewPage()
 		}
 
-		p := c.getActivePage()
-		err := blk.drawToPage(p)
-		if err != nil {
-			return err
+		page := c.getActivePage()
+		if pageBlock, ok := c.pageBlocks[page]; ok {
+			if err := pageBlock.mergeBlocks(block); err != nil {
+				return err
+			}
+			if err := mergeResources(block.resources, pageBlock.resources); err != nil {
+				return err
+			}
+		} else {
+			c.pageBlocks[page] = block
 		}
 	}
 

creator/creator_test.go

@@ -2740,11 +2740,17 @@ func TestCompressStreams(t *testing.T) {
 		c.Draw(p)
 		//c.NewPage()
 
-		page := c.pages[0]
-		// Need to add Arial to the page resources to avoid generating invalid PDF (avoid build fail).
-		times := model.NewStandard14FontMustCompile(model.TimesRomanName)
-		page.Resources.SetFontByName("Times", times.ToPdfObject())
-		rawContent := `
+		c.SetPdfWriterAccessFunc(func(w *model.PdfWriter) error {
+			page := c.pages[0]
+
+			// Need to add Times to the page resources as it is used in the raw content stream.
+			times, err := model.NewStandard14Font(model.TimesRomanName)
+			if err != nil {
+				return err
+			}
+			page.Resources.SetFontByName("Times", times.ToPdfObject())
+
+			rawContent := `
 BT
 /Times 56 Tf
 20 600 Td
@@ -2762,15 +2768,17 @@ BT
 (example text)'
 ET
 `
-		{
+
 			cstreams, err := page.GetContentStreams()
 			if err != nil {
-				panic(err)
+				return err
 			}
 			cstreams = append(cstreams, rawContent)
+
 			// Set streams with raw encoder (not encoded).
 			page.SetContentStreams(cstreams, core.NewRawEncoder())
-		}
+			return nil
+		})
 
 		return c
 	}