Python中用Barcode库生成条码后添加商品名称的字体适配问题

我用Python的Barcode库生成条码，核心代码如下：

barcodes = CompanyBarcodes.objects.filter(asn_id__asn_number=asn_id,
                                          company=company,
                                          product__asset_category__in=cat_ids
    ).prefetch_related('company', 'product', 'grn_id', 'asn_id', 'itemGroup')

items = []

for i in barcodes:
    items.append({'bar': i.barcode, 'name': str(i.product.name)
                  + " - " + str(i.product.sku)})

alist = []

for item in items:
    print("item", item)
    EAN = barcode.get_barcode_class('code128')
    d = {'module_width': 0.15,
         'module_height': 2.0,
         'quiet_zone': 0.5,
         'text_distance': 1.5,
         'font_size': 3,
         'text_line_distance': 3,
         'dpi': 900}
    w = ImageWriter(d)
    ean = EAN(item['bar'], writer=ImageWriter())
    a = ean.save(item['bar'], options=d)

现在需要把items里的商品名称（name字段）添加到生成的条码图片中，我尝试了以下代码，但添加的文字尺寸过小，且和条码自带的字体不一致：

with open(a, 'rb') as image:
    img = Image.open(image)

    # Create a drawing context on the image
    draw = ImageDraw.Draw(img)

    # Use the same font as the original barcode image
    font = ImageFont.load_default()

    # Set the font size
    font_size = 10  # You can adjust the font size as needed

    # Calculate the position to center the text
    text = item['name']
    text_width, text_height = draw.textsize(text, font=font)
    image_width, image_height = img.size
    text_x = (image_width - text_width) / 2
    text_y = image_height - text_height - 5  # Adjust the vertical position as needed

    # Draw the text on the image
    draw.text((text_x, text_y), text, fill=(0, 0, 0), font=font)  # You can adjust the fill color

    # Save the modified image
    img.save(a)  # Overwrite the original image with the changes
    encoded_image = base64.b64encode(open(a, 'rb').read()).decode('utf-8')
    alist.append({'image': encoded_image, **item})

解决方案 #

1. 匹配条码使用的字体 #

Barcode库默认使用FreeMono等宽字体（和条码下方数字的字体一致），不要用ImageFont.load_default()加载默认字体，直接指定同类型等宽字体即可。如果系统没有FreeMono，可替换为Courier New等系统自带的等宽字体。

2. 按DPI换算字体大小 #

因为生成条码时设置了dpi=900，字体大小需要按这个DPI换算（条码的font_size=3对应900DPI下的3*900/72≈38号字体），避免文字过小。

修改后的完整代码 #

将添加文字的代码替换为以下内容：

from PIL import Image, ImageDraw, ImageFont

# 获取条码生成时的DPI配置
dpi = d['dpi']
# 按DPI换算字体大小，和条码文字尺寸匹配
font_size = int(d['font_size'] * dpi / 72)

# 加载和条码一致的等宽字体
try:
    font = ImageFont.truetype("FreeMono.ttf", font_size)
except IOError:
    # 兜底用Courier New等宽字体
    font = ImageFont.truetype("Courier New", font_size)
except:
    # 极端情况用默认字体，但按DPI放大
    font = ImageFont.load_default(size=font_size)

with open(a, 'rb') as image:
    img = Image.open(image)
    draw = ImageDraw.Draw(img)
    text = item['name']
    
    # 计算文字位置：水平居中，垂直在条码下方预留足够间距
    text_width, text_height = draw.textsize(text, font=font)
    image_width, image_height = img.size
    text_x = (image_width - text_width) // 2
    # 按DPI换算偏移量，避免在不同分辨率下位置偏移
    text_y = image_height - text_height - int(10 * dpi / 72)
    
    # 绘制文字，颜色和条码文字保持一致（黑色）
    draw.text((text_x, text_y), text, fill=(0, 0, 0), font=font)
    
    # 保存时指定DPI，避免图片缩放变形
    img.save(a, dpi=(dpi, dpi))
    encoded_image = base64.b64encode(open(a, 'rb').read()).decode('utf-8')
    alist.append({'image': encoded_image, **item})

额外优化点 #

• 生成条码时复用已定义的ImageWriter实例，避免参数不一致：

  ean = EAN(item['bar'], writer=w)  # 用之前定义的w，而非重新创建ImageWriter()
  a = ean.save(item['bar'], options=d)
  

• 若商品名称过长，可添加自动换行逻辑：

  # 按图片宽度自动拆分文字
  def wrap_text(text, font, max_width):
      lines = []
      current_line = ""
      for word in text.split():
          test_line = current_line + word + " "
          test_width, _ = draw.textsize(test_line, font=font)
          if test_width <= max_width:
              current_line = test_line
          else:
              lines.append(current_line.strip())
              current_line = word + " "
      lines.append(current_line.strip())
      return lines
  
  # 应用换行逻辑，左右预留边距
  wrapped_lines = wrap_text(text, font, image_width - int(20 * dpi / 72))
  total_text_height = text_height * len(wrapped_lines)
  # 调整垂直位置，让所有换行文字居中
  text_y = image_height - total_text_height - int(10 * dpi / 72)
  
  # 逐行绘制文字
  for line in wrapped_lines:
      line_width, _ = draw.textsize(line, font=font)
      line_x = (image_width - line_width) // 2
      draw.text((line_x, text_y), line, fill=(0,0,0), font=font)
      text_y += text_height
  

内容的提问来源于stack exchange，提问作者Rahul Sharma