Add support for monochromatic images (PIL image.mode == '1')

CHANGELOG.md

@@ -17,6 +17,8 @@ in order to get warned about deprecated features used in your code.
 This can also be enabled programmatically with `warnings.simplefilter('default', DeprecationWarning)`.
 
 ## [2.5.8] - not released yet
+### Added
+- support for monochromatic images (PIL image.mode == '1')
 
 ## [2.5.7] - 2022-09-08
 ### Changed

fpdf/image_parsing.py

@@ -2,6 +2,7 @@
 from io import BytesIO
 import base64
 from urllib.request import urlopen
+from math import ceil
 
 try:
     from PIL import Image
@@ -70,12 +71,15 @@ def get_img_info(img, image_filter="AUTO", dims=None):
     if img.mode in ("P", "PA") and image_filter != "FlateDecode":
         img = img.convert("RGBA")
 
-    if img.mode not in ("L", "LA", "RGB", "RGBA", "P", "PA"):
+    if img.mode not in ("1", "L", "LA", "RGB", "RGBA", "P", "PA"):
         img = img.convert("RGBA")
 
     w, h = img.size
     info = {}
-    if img.mode == "L":
+    if img.mode == "1":
+        dpn, bpc, colspace = 1, 1, "DeviceGray"
+        info["data"] = _to_data(img, image_filter)
+    elif img.mode == "L":
         dpn, bpc, colspace = 1, 8, "DeviceGray"
         info["data"] = _to_data(img, image_filter)
     elif img.mode == "LA":
@@ -171,8 +175,11 @@ def _to_zdata(img, remove_slice=None, select_slice=None):
     if select_slice:
         data = data[select_slice]
     # Left-padding every row with a single zero:
-    channels_count = len(data) // (img.size[0] * img.size[1])
-    loop_incr = img.size[0] * channels_count + 1
+    if img.mode == "1":
+        loop_incr = ceil(img.size[0] / 8) + 1
+    else:
+        channels_count = len(data) // (img.size[0] * img.size[1])
+        loop_incr = img.size[0] * channels_count + 1
     i = 0
     while i < len(data):
         data[i:i] = b"\0"

test/image/image_info.json

@@ -2,10 +2,10 @@
     "basi0g01.png": {
         "w": 32,
         "h": 32,
-        "cs": "DeviceRGB",
-        "bpc": 8,
+        "cs": "DeviceGray",
+        "bpc": 1,
         "f": "FlateDecode",
-        "dp": "/Predictor 15 /Colors 3 /BitsPerComponent 8 /Columns 32",
+        "dp": "/Predictor 15 /Colors 1 /BitsPerComponent 1 /Columns 32",
         "trns": ""
     },
     "basi0g02.png": {
@@ -145,10 +145,10 @@
     "basn0g01.png": {
         "w": 32,
         "h": 32,
-        "cs": "DeviceRGB",
-        "bpc": 8,
+        "cs": "DeviceGray",
+        "bpc": 1,
         "f": "FlateDecode",
-        "dp": "/Predictor 15 /Colors 3 /BitsPerComponent 8 /Columns 32",
+        "dp": "/Predictor 15 /Colors 1 /BitsPerComponent 1 /Columns 32",
         "trns": ""
     },
     "basn0g02.png": {
@@ -1535,4 +1535,4 @@
         "dp": "/Predictor 15 /Colors 3 /BitsPerComponent 8 /Columns 32",
         "trns": ""
     }
-}
+}

test/image/image_types/test_insert_images.py

@@ -60,6 +60,13 @@ def test_insert_png(tmp_path):
     assert_pdf_equal(pdf, HERE / "image_types_insert_png.pdf", tmp_path)
 
 
+def test_insert_png_monochromatic(tmp_path):
+    pdf = fpdf.FPDF()
+    pdf.add_page()
+    pdf.image(HERE / "../png_test_suite/basi0g01.png", x=15, y=15, h=140)
+    assert_pdf_equal(pdf, HERE / "image_types_insert_png_monochromatic.pdf", tmp_path)
+
+
 def test_insert_png_alpha(tmp_path):
     pdf = fpdf.FPDF()
     pdf.compress = False