给 reportlab.lib.utils.ImageReader 一个字节

Question

我了解到您可以使用类似字节的对象来 reportlab.lib.utils.ImageReader()。如果我在文件路径中读取它工作正常，但我想使用类似字节的对象，这样我就可以将我想要的绘图保存在内存中，而不必不断地在驱动器上保存更新的绘图。

这是我找到将图像转换为字符串的代码的地方 https://www.programcreek.com/2013/09/convert-image-to-string-in-python/

这是一个如何使用 BytesIO 作为 ImageReader() 输入的示例

这个class用于制作绘图并通过BytesIO()将其保存到内存中。字符串是我稍后要传递的值

#imports

import PyPDF2
from io import BytesIO

from reportlab.lib import utils
from reportlab.lib.pagesizes import landscape, letter
from reportlab.platypus import (Image, SimpleDocTemplate,
                                Paragraph, Spacer)
from reportlab.lib.styles import getSampleStyleSheet
from reportlab.lib.units import inch, mm
import datetime
import os
import csv
import io
import base64
import urllib
from django.contrib import admin
from django.forms import model_to_dict
from django.http import HttpResponse
from django.urls import path
from django.views.decorators.csrf import csrf_protect
from django.utils.decorators import method_decorator
from reporting import models, functions, functions2
import matplotlib
matplotlib.use('agg')
from matplotlib import pyplot as plt
import numpy as np

def make_plot(data):
    items = [tuple(item) for item in data.items()]
    keys = [item[0] for item in items]
    vals = [item[1] for item in items]
    fig, ax = plt.subplots()
    ind = np.arange(len(keys))  # the x locations for the groups
    width = 0.35  # the width of the bars
    rects1 = ax.bar(ind - width/2, vals, width)
    ax.set_ylabel('Count')
    ax.set_xticks(ind)
    ax.set_xticklabels(keys)
    buf = io.BytesIO()
    fig.savefig(buf, format='png')
    buf.seek(0)
    string = base64.b64encode(buf.read())
    return 'data:image/png;base64,' + urllib.parse.quote(string), string

这是显示信息如何移动到错误发生位置的最少代码。

class ProgressReportAdmin(ReadOnlyAdmin):
    current_extra_context = None

    @csrf_protect_m
    def changelist_view(self, request, extra_context=None):
       plot = make_plot(data)
       self.current_extra_context = plot[1]

    def export(self, request):
       image = self.current_extra_context
       pdf = functions.LandscapeMaker(image, fname, rotate=True)
       pdf.save()

这是错误发生的地方，在scaleImage函数中

class LandscapeMaker(object):
    def __init__(self, image_path, filename, rotate=False):
           self.pdf_file = os.path.join('.', 'media', filename)
           self.logo_path = image_path
           self.story = [Spacer(0, 1*inch)]

    def save(self):
        fileObj = BytesIO()
        self.doc = SimpleDocTemplate(fileObj, pagesize=letter,
                                         leftMargin=1*inch)
        self.doc.build(self.story,
                       onFirstPage=self.create_pdf)

    def create_pdf(self, canvas, doc):
        logo = self.scaleImage(self.logo_path)

    def scaleImage(self, img_path, maxSize=None):
        #Error1 occurs on
        img = utils.ImageReader(img_path)
        img.fp.close()

        #Error2
        #image = BytesIO(img_path)
        #img = utils.ImageReader(image)
        #img.fp.close()

对于错误 1，我收到：

raise IOError('Cannot open resource "%s"' % name)
img = utils.ImageReader(img_path)
"OSError: Cannot open resource "b'iVBORw0KGgoAAA' etc.,

我收到错误 2

OSError: cannot identify image file <_io.BytesIO object at 0x7f8e4057bc50>
cannot identify image file <_io.BytesIO object at 0x7f8e4057bc50>
fileName=<_io.BytesIO object at 0x7f8e4057bc50> identity=[ImageReader@0x7f8e43fd15c0]

Answer 1

我认为你必须以某种方式将 buff 传递给 ImageReader。

我正在使用此功能来保存和绘制我用 matplotlib 生成的图形，它非常适合我。

seek(offset, whence=SEEK_SET) 将流位置更改为给定的偏移量。行为取决于 whence 参数。 whence 的默认值为 SEEK_SET.

getvalue() 不工作，除了 seek(0)

def save_and_draw(fig, x_img, y_img, width_img=width_img, height_img=height_img): 
    imgdata = BytesIO()
    fig.savefig(imgdata, format='png')
    imgdata.seek(0)
    imgdata = ImageReader(imgdata)
            
    self.c.drawImage(imgdata, x_img, y_img, width_img, height_img)
    plt.close(fig)

给 reportlab.lib.utils.ImageReader 一个字节

give a bytes to reportlab.lib.utils.ImageReader

python

django

file

reportlab