Clipart and text shadows corrected / implemented

clipart/areas.py

@@ -2,16 +2,25 @@
 
 import logging
 
+from PIL import Image
 from reportlab.lib.utils import ImageReader
 
 from .catalog import getClipConfig, loadClipart
+from conversionState import ConversionState
 from renderContext import RenderContext
 
 
+def _hasEnabledShadow(decoration):
+    """Return whether ``decoration`` contains a CEWE-enabled shadow."""
+    return (decoration is not None
+            and any(shadow.get('shadowEnabled') in (None, '1')
+                    for shadow in decoration.findall('shadow')))
+
+
 def processAreaClipartTag(clipartElement, areaHeight, areaRot, areaWidth, pdf, transx, transy,
                           clipArtDecoration, context: RenderContext,
-                          borderProcessor):
-    """Render one clipart area and its optional border."""
+                          state: ConversionState, shadowProcessor, borderProcessor):
+    """Render one clipart area and its optional decorations."""
     clipartID = int(clipartElement.get('designElementId'))
     if clipartID == 0:
         return
@@ -29,11 +38,13 @@ def processAreaClipartTag(clipartElement, areaHeight, areaRot, areaWidth, pdf, t
 
     colorReplacements, flipX, flipY = getClipConfig(clipartElement)
     insertClipartFile(fileName, colorReplacements, transx, areaWidth, areaHeight, alpha, pdf,
-                      transy, areaRot, flipX, flipY, clipArtDecoration, context, borderProcessor)
+                      transy, areaRot, flipX, flipY, clipArtDecoration, context, state,
+                      shadowProcessor, borderProcessor)
 
 
 def insertClipartFile(fileName, colorReplacements, transx, areaWidth, areaHeight, alpha, pdf,
                       transy, areaRot, flipX, flipY, decoration, context: RenderContext,
+                      state: ConversionState | None = None, shadowProcessor=None,
                       borderProcessor=None):
     """Rasterise a clipart file and draw it at the supplied area geometry."""
     newWidth = int(0.5 + areaWidth * context.image_resolution / 254.0)
@@ -48,9 +59,19 @@ def insertClipartFile(fileName, colorReplacements, transx, areaWidth, areaHeight
         clipart.replaceColors(colorReplacements)
 
     clipart.convertToPngInBuffer(newWidth, newHeight, alpha, flipX, flipY)
+    clipartImage = None
+    if _hasEnabledShadow(decoration) and shadowProcessor is not None and state is not None:
+        # Use the rasterised SVG's alpha silhouette.  In particular, open
+        # artwork (for example an arrow) must not cast a rectangular shadow.
+        clipartImage = Image.open(clipart.pngMemFile).convert('RGBA')
+        clipartImage.load()
+        clipart.pngMemFile.seek(0)
     logging.debug(f"Clipart file: {fileName}")
     pdf.translate(transx, transy)
     pdf.rotate(-areaRot)
+    if clipartImage is not None:
+        shadowProcessor(decoration, areaHeight, areaWidth, pdf, context, state,
+                        clipartImage, areaWidth, areaHeight, areaRotation=areaRot)
     pdf.drawImage(ImageReader(clipart.pngMemFile),
                   context.mcf_to_reportlab * -0.5 * areaWidth,
                   context.mcf_to_reportlab * -0.5 * areaHeight,

decorations/shadows.py

@@ -53,10 +53,11 @@ def drawBlurredImageShadow(pdf, im, imgCropWidth_mcfunit,
     # was downsampled earlier in processAreaImageTag.
     pixelsPerMcfunit = im.width / imgCropWidth_mcfunit
 
-    # CEWE's displayed shadow expands by about three tenths of the nominal
-    # width on each side. This was calibrated against the width-only test page
-    # (0 .. 10 mm); the old ReportLab Table is noticeably larger at high values.
-    spreadRadius_px = int(round(
+    # CEWE's displayed shadow protrudes by about three tenths of the nominal
+    # width on each side.  It enlarges the shadow's bounding box rather than
+    # thickening every opaque pixel.  The distinction is invisible for a
+    # solid rectangle but essential for open artwork such as arrows.
+    spreadOutset_px = int(round(
         shadowWidth_mcfunit * pixelsPerMcfunit * 0.30
     ))
 
@@ -68,18 +69,22 @@ def drawBlurredImageShadow(pdf, im, imgCropWidth_mcfunit,
     # Keep the fractional radius: rounding it would make several of CEWE's
     # small blur settings render identically at the configured image DPI.
     blurRadius_px = shadowBlur_mcfunit * pixelsPerMcfunit * 0.5
-    padding_px = spreadRadius_px + int(np.ceil(3 * blurRadius_px))
+    blurPadding_px = int(np.ceil(3 * blurRadius_px))
+    padding_px = spreadOutset_px + blurPadding_px
 
     alpha = im.getchannel('A')
     shadowAlpha = Image.new(
         'L', (im.width + 2 * padding_px, im.height + 2 * padding_px), 0
     )
-    shadowAlpha.paste(alpha, (padding_px, padding_px))
-
-    if spreadRadius_px > 0:
-        shadowAlpha = shadowAlpha.filter(
-            ImageFilter.MaxFilter(2 * spreadRadius_px + 1)
-        )
+    if spreadOutset_px > 0:
+        # Put a scaled copy of the alpha silhouette into the enlarged shadow
+        # bounds.  A morphological max filter would make an open SVG's thin
+        # strokes dramatically fatter, unlike CEWE's ``Utstikk`` control.
+        alpha = alpha.resize(
+            (im.width + 2 * spreadOutset_px,
+             im.height + 2 * spreadOutset_px),
+            Image.Resampling.LANCZOS)
+    shadowAlpha.paste(alpha, (blurPadding_px, blurPadding_px))
 
     if blurRadius_px > 0:
         shadowAlpha = shadowAlpha.filter(ImageFilter.GaussianBlur(blurRadius_px))

pageElements.py

@@ -119,7 +119,8 @@ def processElements(additional_fonts, fotobook, imagedir,
             for clipartElement in area.findall('clipart'):
                 processAreaClipartTag(
                     clipartElement, areaHeight, areaRot, areaWidth, pdf,
-                    transCx, transCy, decoration, context,
+                    transCx, transCy, decoration, context, state,
+                    processDecorationShadow,
                     lambda decoration, height, width, canvas:
                     processDecorationBorders(decoration, height, width,
                                              canvas, context))