Pad Folder Of Cropped Images To Maximum Width

Question

Is there a way to take a folder of cropped images, take the maximum width of them, and pad the rest with white on the right, so that they are all the same width?

I have written a python script, that takes a folder of images, crops their white border away, and in a second step rescales them into a PDF. The images are lemmas from a script, that is why not all of them fill the whole linewidth.

The issue is, that if an image does not fill the linewidth before cropping, the white is cropped automatically away, and then the imagewidth is too narrow, and if it is then pasted into the PDF, it is upscaled, and way out of proportion. Therefore it would probably be best to crop them first, and then pad them, and afterwards continue with the PDF creation.

Below is the whole code, altough only the trim and crop methods would probably be affected by this question.

# All the necessary parameters are accessible after line 55,
# but can of course be changed manually in the Code


# imports for the crop, rename to avoid conflict with reportlab Image import
from PIL import Image as imgPIL
from PIL import ImageChops
import os.path, sys

# import for the PDF creation
import glob
from reportlab.lib.pagesizes import A4
from reportlab.lib import utils
from reportlab.platypus import Image, SimpleDocTemplate, Spacer
from reportlab.lib.units import mm, inch

# get os path for Cropping
path = (os.path.dirname(os.path.abspath("cropPDF.py")))
dirs = os.listdir(path)


def trim(im, border="white"):
    bg = imgPIL.new(im.mode, im.size, border)
    diff = ImageChops.difference(im, bg)
    bbox = diff.getbbox()
    if bbox:
        return im.crop(bbox)


def crop():
    for item in dirs:
        try:
            fullpath = os.path.join(path, item)
            if os.path.isfile(fullpath):
                im = imgPIL.open(fullpath)
                f, e = os.path.splitext(fullpath)
                imCrop = trim(im, "white")
                imCrop.save(f + ".png", "PNG", quality=100)
        except:
            pass


def add_page_number(canvas, doc):
    canvas.saveState()
    canvas.setFont('Times-Roman', numberFontSize)
    page_number_text = "%d" % (doc.page)
    canvas.drawCentredString(
        pageNumberSpacing * mm,
        pageNumberSpacing * mm,
        page_number_text
    )
    canvas.restoreState()


#############################

executeCrop = True

outputName = "output.pdf"

margin = 0.5
imageWidthDefault = 550
spacerHeight = 7
scalingIfImageTooTall = 0.95  # larger than 95 can result in an empty page after the image

includePagenumbers = True
numberFontSize = 10
pageNumberSpacing = 5

############################

if executeCrop:
    crop()

filelist = glob.glob("*.png")  # Get a list of files in the current directory
filelist.sort()

doc = SimpleDocTemplate(
    outputName,
    topMargin=margin * mm,
    leftMargin=margin * mm,
    rightMargin=margin * mm,
    bottomMargin=margin * mm,
    pagesize=A4
)

story = []  # create the list of images for the PDF

for fn in filelist:
    img = utils.ImageReader(fn)
    img_width, img_height = img.getSize()  # necessary for the aspect ratio
    aspect = img_height / float(img_width)

    documentHeight = doc.height

    imageWidth = imageWidthDefault
    imageHeight = imageWidth * aspect

    if imageHeight > documentHeight:
        imageHeight = documentHeight * scalingIfImageTooTall
        imageWidth = imageHeight / aspect

    img = Image(
        fn,
        width=imageWidth,
        height=imageHeight
    )
    story.append(img)
    space = Spacer(width=0, height=spacerHeight)
    story.append(space)

if includePagenumbers and not len(filelist) == 0:  # if pagenumbers are desired, or not
    doc.build(
        story,
        onFirstPage=add_page_number,
        onLaterPages=add_page_number,
    )
elif not len(filelist) == 0:
    doc.build(story)
else:  # to prevent an empty PDF that can't be opened
    print("no files found")

Answer 1

I have now created a solution using from PIL import ImageOps

These two new Methods provide the needed functionality, the first one finds the max width of all images, and the second one creates a blank image for each image in the folder, and pastes the original overtop:

def findMaxWidth():
maxWidth = 0
for item in dirs:
    try:
        fullpath = os.path.join(path, item)
        if os.path.isfile(fullpath):
            im = imgPIL.open(fullpath)
            maxWidth = max(maxWidth, im.size[0])
    except:
        pass
return maxWidth


def padImages():
maxWidth = findMaxWidth()
for item in dirs:
    try:
        fullpath = os.path.join(path, item)
        if os.path.isfile(fullpath):
            im = imgPIL.open(fullpath)
            f, e = os.path.splitext(fullpath)

            width,height = im.size #get the image dimensions, the height is needed for the blank image

            image = imgPIL.new('RGB', (maxWidth, height), (255, 255, 255)) #create a white image with the max width         
            image.paste(im, (0,0) ) #paste the original image overtop the blank one, flush on the left side
            image.save(f + ".png", "PNG", quality=100)
    except:
        pass