在 Python 中创建 PNG 文件

Question

我有一个应用程序，我希望能够从 Python 中的数据生成 PNG 图像。我做了一些搜索，发现“PIL”看起来相当过时。还有其他图书馆更适合这个吗？

Answer 1

简单的 PNG 文件可以很容易地从纯 Python 代码生成 - 您所需要的只是标准 zlib 模块和一些字节编码来写入块。这是一个完整的示例，普通读者可以将其用作自己的 png 生成器的入门：

#! /usr/bin/python
""" Converts a list of list into gray-scale PNG image. """
__copyright__ = "Copyright (C) 2014 Guido Draheim"
__licence__ = "Public Domain"

import zlib
import struct

def makeGrayPNG(data, height = None, width = None):
    def I1(value):
        return struct.pack("!B", value & (2**8-1))
    def I4(value):
        return struct.pack("!I", value & (2**32-1))
    # compute width&height from data if not explicit
    if height is None:
        height = len(data) # rows
    if width is None:
        width = 0
        for row in data:
            if width < len(row):
                width = len(row)
    # generate these chunks depending on image type
    makeIHDR = True
    makeIDAT = True
    makeIEND = True
    png = b"\x89" + "PNG\r\n\x1A\n".encode('ascii')
    if makeIHDR:
        colortype = 0 # true gray image (no palette)
        bitdepth = 8 # with one byte per pixel (0..255)
        compression = 0 # zlib (no choice here)
        filtertype = 0 # adaptive (each scanline seperately)
        interlaced = 0 # no
        IHDR = I4(width) + I4(height) + I1(bitdepth)
        IHDR += I1(colortype) + I1(compression)
        IHDR += I1(filtertype) + I1(interlaced)
        block = "IHDR".encode('ascii') + IHDR
        png += I4(len(IHDR)) + block + I4(zlib.crc32(block))
    if makeIDAT:
        raw = b""
        for y in xrange(height):
            raw += b"\0" # no filter for this scanline
            for x in xrange(width):
                c = b"\0" # default black pixel
                if y < len(data) and x < len(data[y]):
                    c = I1(data[y][x])
                raw += c
        compressor = zlib.compressobj()
        compressed = compressor.compress(raw)
        compressed += compressor.flush() #!!
        block = "IDAT".encode('ascii') + compressed
        png += I4(len(compressed)) + block + I4(zlib.crc32(block))
    if makeIEND:
        block = "IEND".encode('ascii')
        png += I4(0) + block + I4(zlib.crc32(block))
    return png

def _example():
    with open("cross3x3.png","wb") as f:
        f.write(makeGrayPNG([[0,255,0],[255,255,255],[0,255,0]]))

Answer 2

这是一个 Python3 示例：

import png

width = 255
height = 255
img = []
for y in range(height):
    row = ()
    for x in range(width):
        row = row + (x, max(0, 255 - x - y), y)
    img.append(row)
with open('gradient.png', 'wb') as f:
    w = png.Writer(width, height, greyscale=False)
    w.write(f, img)

Answer 3

还有其他库更适合这个吗？

png 包将是一个合理的常见选择。

这是项目描述：

PyPNG 允许使用纯 Python 读取和写入 PNG 图像文件。

Answer 4

经过一番搜索后，我找到了这个网站： https://www.daniweb.com/programming/software-development/code/454765/save-a-pygame-drawing。它只是使用旧的 pygame。

第 37 行：(pg.image.save(win, fname)) 将 pygame 表面上绘制的任何内容保存为文件。

编辑

这是实际的代码：

"""pg_draw_circle_save101.py
draw a blue solid circle on a white background
save the drawing to an image file
for result see http://prntscr.com/156wxi
tested with Python 2.7 and PyGame 1.9.2 by vegaseat  16may2013
"""

import pygame as pg

# pygame uses (r, g, b) color tuples
white = (255, 255, 255)
blue = (0, 0, 255)

width = 300
height = 300

# create the display window
win = pg.display.set_mode((width, height))
# optional title bar caption
pg.display.set_caption("Pygame draw circle and save")
# default background is black, so make it white
win.fill(white)

# draw a blue circle
# center coordinates (x, y)
center = (width//2, height//2)
radius = min(center)
# width of 0 (default) fills the circle
# otherwise it is thickness of outline
width = 0
# draw.circle(Surface, color, pos, radius, width)
pg.draw.circle(win, blue, center, radius, width)

# now save the drawing
# can save as .bmp .tga .png or .jpg
fname = "circle_blue.png"
pg.image.save(win, fname)
print("file {} has been saved".format(fname))

# update the display window to show the drawing
pg.display.flip()


# (press escape key or click window title bar x to exit)
while True:
for event in pg.event.get():
    if event.type == pg.QUIT:
        # most reliable exit on x click
        pg.quit()
        raise SystemExit
    elif event.type == pg.KEYDOWN:
        # optional exit with escape key
        if event.key == pg.K_ESCAPE:
            pg.quit()
            raise SystemExit

Answer 5

我知道这个问题是 9 年前提出的，但在 Python 3.8 时代，你可以以“写入二进制”模式打开文件：

f = open("filename.png", 'wb')
# data being whatever data you wanted to write
f.write(data)