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theonlypwner/randompng.py

Last active August 25, 2023 09:58
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  1. theonlypwner revised this gist Feb 26, 2016. 1 changed file with 13 additions and 0 deletions.
    13 changes: 13 additions & 0 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -99,6 +99,19 @@ def rPNG():
    filtermethod = 0 # adaptive (only supported method)
    interlaced = 0 # no

    maxEntropyBits = DEPTH * IMAGE_W * IMAGE_H
    print("Projected (maximum) entropy: {0} bits ({1} bytes)".format(
    maxEntropyBits,
    (maxEntropyBits + 7) >> 3,
    ))
    approxFileSize = (DEPTH * (IMAGE_W + 1) * IMAGE_H * BLOCK_W * BLOCK_H) >> 10 # approx / 1032
    approxFileSize += 64 # FIXME
    approxFileSize += maxEntropyBits
    print("Estimated file size: {0} bits ({1} bytes)".format(
    approxFileSize,
    (approxFileSize + 7) >> 3,
    ))

    if DEPTH == 1:
    bytesPerRow = (DEPTH * IMAGE_W + 7) >> 3
    else:
  2. theonlypwner revised this gist Feb 26, 2016. 1 changed file with 9 additions and 4 deletions.
    13 changes: 9 additions & 4 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -39,6 +39,8 @@ def B(x):
    def I4(x):
    return struct.pack(">I", x & 0xFFFFFFFF)

    zero16KiB = b"\0" * 16383

    class CompressedPixelWriter:
    compressor = zlib.compressobj(9) # max compression
    out = lambda: None
    @@ -56,11 +58,14 @@ def writeRaw(self, b):
    def write(self, b):
    self.writeRaw(self.compressor.compress(b))

    # memory-optimized write() for many zero bytes
    # improved write() for many zero bytes
    def writez(self, num):
    for i in range(num):
    self.out(self.compressor.compress(b"\0"))
    self.crc32 = zlib.crc32(b"\0", self.crc32)
    for i in range(num >> 14):
    self.out(self.compressor.compress(zero16KiB))
    self.crc32 = zlib.crc32(zero16KiB, self.crc32)
    num &= 0x3FFF
    self.out(self.compressor.compress(b"\0" * num))
    self.crc32 = zlib.crc32(b"\0" * num, self.crc32)
    self.length += num

    def writePixels(self):
  3. theonlypwner revised this gist Feb 26, 2016. 1 changed file with 13 additions and 16 deletions.
    29 changes: 13 additions & 16 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -78,7 +78,9 @@ def rPNG():
    height = IMAGE_H * BLOCK_H
    bitdepth = 8 # [bit/sample]
    if DEPTH == 1:
    # bitdepth = 1 # TODO
    bitdepth = 1
    if BLOCK_W > 1:
    raise NotImplementedError("For bit depth of 1, only blocks of width 1 are supported")
    colortype = 0
    elif DEPTH == 8:
    colortype = 0
    @@ -93,23 +95,18 @@ def rPNG():
    interlaced = 0 # no

    if DEPTH == 1:
    bytesPerPixel = 1
    def imageFilter(b):
    b = bytearray(b)
    for i in range(len(b)):
    b[i] = -(b[i] & 0x1) & 0xFF
    return bytes(b)
    bytesPerRow = (DEPTH * IMAGE_W + 7) >> 3
    else:
    bytesPerPixel = DEPTH >> 3
    imageFilter = bytes
    if BLOCK_W > 1:
    pixelPadding = bytesPerPixel * (BLOCK_W - 1)
    bytesPerRow = bytesPerPixel * IMAGE_W
    rowPadding = bytesPerRow * BLOCK_W

    class RandomPixelWriter(CompressedPixelWriter):

    def writePixels(self):
    # Bad practice: using globals
    # - BLOCK_W, BLOCK_H, IMAGE_W, IMAGE_H (sort of OK)
    # - bytesPerPixel
    # - imageFilter
    # This method uses globals, which is probably bad...

    for y in range(IMAGE_H):
    # Write scanline
    @@ -119,16 +116,16 @@ def writePixels(self):
    for x in range(IMAGE_W):
    # There is no need to subtract from prev,
    # because random differences are still random.
    self.write(imageFilter(urandom(bytesPerPixel)))
    self.writez(bytesPerPixel * (BLOCK_W - 1))
    self.write(urandom(bytesPerPixel))
    self.writez(pixelPadding)
    else:
    self.write(b"\x00") # no PNG filter
    self.write(imageFilter(urandom(bytesPerPixel * IMAGE_W)))
    self.write(urandom(bytesPerRow))

    # Repeat previous scanline, at least one time, if needed
    for i in range(1, BLOCK_H):
    self.write(b"\x02") # Up filter
    self.writez(bytesPerPixel * IMAGE_W * BLOCK_W)
    self.writez(rowPadding)

    with open(OUTPUT_FILE, "wb") as f:
    # Signature
  4. theonlypwner revised this gist Feb 24, 2016. 1 changed file with 23 additions and 27 deletions.
    50 changes: 23 additions & 27 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -21,13 +21,12 @@
    OUTPUT_FILE = "r.png" # Do I really need to explain this?
    BLOCK_W, BLOCK_H = 8, 8 # block size [pixels]
    IMAGE_W, IMAGE_H = 240, 135 # image size [blocks]
    DEPTH = 3
    DEPTH = 24
    # Color depth [bytes/pixel]
    # 1 Grayscale
    # 3 RGB
    # 4 RGBA
    # -1 Black and White
    # -3 Black and White (as RGB)
    # 1 Black and White
    # 8 Grayscale
    # 24 RGB
    # 32 RGBA

    # Script
    from os import urandom
    @@ -57,7 +56,7 @@ def writeRaw(self, b):
    def write(self, b):
    self.writeRaw(self.compressor.compress(b))

    # optimized write() for many zero bytes
    # memory-optimized write() for many zero bytes
    def writez(self, num):
    for i in range(num):
    self.out(self.compressor.compress(b"\0"))
    @@ -78,61 +77,58 @@ def rPNG():
    width = IMAGE_W * BLOCK_W
    height = IMAGE_H * BLOCK_H
    bitdepth = 8 # [bit/sample]
    if DEPTH == 1 or DEPTH == -1:
    if DEPTH == 1:
    # bitdepth = 1 # TODO
    colortype = 0
    elif DEPTH == 3 or DEPTH == -3:
    elif DEPTH == 8:
    colortype = 0
    elif DEPTH == 24:
    colortype = 2
    elif DEPTH == 4:
    elif DEPTH == 32:
    colortype = 6
    else:
    raise NotImplementedError("Unsupported color depth " + DEPTH)
    raise NotImplementedError("Unsupported color depth {0}".format(DEPTH))
    compresstype = 0 # zlib (only supported method)
    filtermethod = 0 # adaptive (only supported method)
    interlaced = 0 # no

    if DEPTH < 1:
    bitsPerPixel = 1
    if DEPTH == 1:
    bytesPerPixel = 1
    def imageFilter(b):
    b = bytearray(b)
    for i in range(len(b)):
    b[i] = -(b[i] & 0x1) & 0xFF
    return bytes(b)
    BLOCK_W *= -DEPTH
    else:
    bitsPerPixel = DEPTH
    bytesPerPixel = DEPTH >> 3
    imageFilter = bytes

    class RandomPixelWriter(CompressedPixelWriter):

    def writePixels(self):
    # Bad practice: using globals
    # - BLOCK_W, BLOCK_H, IMAGE_W, IMAGE_H (sort of OK)
    # - bitsPerPixel
    # - bytesPerPixel
    # - imageFilter

    if BLOCK_H > 1:
    repeatPrior = bytearray(1 + bitsPerPixel * IMAGE_W * BLOCK_W)
    repeatPrior[0] = 2 # Up filter
    #repeatPrior *= (BLOCK_H - 1)
    repeatPrior = bytes(repeatPrior)

    for y in range(IMAGE_H):
    # Write scanline
    if BLOCK_W > 1:
    self.write(b"\x01") # Sub
    #prev = bytearray(bitsPerPixel)
    #prev = bytearray(bytesPerPixel)
    for x in range(IMAGE_W):
    # There is no need to subtract from prev,
    # because random differences are still random.
    self.write(imageFilter(urandom(bitsPerPixel)))
    self.writez(bitsPerPixel * (BLOCK_W - 1))
    self.write(imageFilter(urandom(bytesPerPixel)))
    self.writez(bytesPerPixel * (BLOCK_W - 1))
    else:
    self.write(b"\x00") # no PNG filter
    self.write(imageFilter(urandom(bitsPerPixel * IMAGE_W)))
    self.write(imageFilter(urandom(bytesPerPixel * IMAGE_W)))

    # Repeat previous scanline, at least one time, if needed
    for i in range(1, BLOCK_H):
    self.write(repeatPrior)
    self.write(b"\x02") # Up filter
    self.writez(bytesPerPixel * IMAGE_W * BLOCK_W)

    with open(OUTPUT_FILE, "wb") as f:
    # Signature
  5. theonlypwner revised this gist Feb 24, 2016. 1 changed file with 1 addition and 1 deletion.
    2 changes: 1 addition & 1 deletion randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -86,7 +86,7 @@ def rPNG():
    colortype = 6
    else:
    raise NotImplementedError("Unsupported color depth " + DEPTH)
    compresstype = 0 # DEFLATE (only supported method)
    compresstype = 0 # zlib (only supported method)
    filtermethod = 0 # adaptive (only supported method)
    interlaced = 0 # no

  6. theonlypwner renamed this gist Feb 23, 2016. 1 changed file with 0 additions and 0 deletions.
    0 output.png → z_output.png
    View file
    File renamed without changes
  7. theonlypwner renamed this gist Feb 23, 2016. 1 changed file with 0 additions and 0 deletions.
    0 r.png → output.png
    View file
    File renamed without changes
  8. theonlypwner revised this gist Feb 23, 2016. 1 changed file with 0 additions and 0 deletions.
    Binary file added r.png
    View file
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  9. theonlypwner revised this gist Feb 23, 2016. 1 changed file with 75 additions and 37 deletions.
    112 changes: 75 additions & 37 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -19,8 +19,8 @@
    # Settings

    OUTPUT_FILE = "r.png" # Do I really need to explain this?
    BLOCK_W, BLOCK_H = 1, 1 # block size [pixels]
    IMAGE_W, IMAGE_H = 1920, 1080 # image size [blocks]
    BLOCK_W, BLOCK_H = 8, 8 # block size [pixels]
    IMAGE_W, IMAGE_H = 240, 135 # image size [blocks]
    DEPTH = 3
    # Color depth [bytes/pixel]
    # 1 Grayscale
    @@ -40,6 +40,38 @@ def B(x):
    def I4(x):
    return struct.pack(">I", x & 0xFFFFFFFF)

    class CompressedPixelWriter:
    compressor = zlib.compressobj(9) # max compression
    out = lambda: None
    length = 0
    crc32 = 0x35AF061E # crc32("IDAT")

    def __init__(self, out):
    self.out = out

    def writeRaw(self, b):
    self.out(b)
    self.length += len(b)
    self.crc32 = zlib.crc32(b, self.crc32)

    def write(self, b):
    self.writeRaw(self.compressor.compress(b))

    # optimized write() for many zero bytes
    def writez(self, num):
    for i in range(num):
    self.out(self.compressor.compress(b"\0"))
    self.crc32 = zlib.crc32(b"\0", self.crc32)
    self.length += num

    def writePixels(self):
    # Empty image data
    pass

    def finalize(self):
    self.writePixels()
    self.writeRaw(self.compressor.flush())

    def rPNG():
    global BLOCK_W

    @@ -70,33 +102,37 @@ def imageFilter(b):
    bitsPerPixel = DEPTH
    imageFilter = bytes

    pixels = bytearray()
    if BLOCK_H > 1:
    repeatPrior = bytearray(1 + bitsPerPixel * IMAGE_W * BLOCK_W)
    repeatPrior[0] = 2 # Up filter
    repeatPrior *= (BLOCK_H - 1)
    if BLOCK_W > 1:
    repeatLeft = bytearray(bitsPerPixel * (BLOCK_W - 1))

    for y in range(IMAGE_H):
    # Write scanline
    if BLOCK_W > 1:
    pixels.append(1) # Sub
    #prev = bytearray(bitsPerPixel)
    for x in range(IMAGE_W):
    # There is no need to subtract from prev,
    # because random differences are still random.
    pixels.extend(imageFilter(urandom(bitsPerPixel)))
    pixels.extend(repeatLeft)
    else:
    pixels.append(0) # no PNG filter
    pixels.extend(imageFilter(urandom(bitsPerPixel * IMAGE_W)))

    # Repeat previous scanline, at least one time, if needed
    if BLOCK_H > 1:
    pixels.extend(repeatPrior)

    pixels = bytes(pixels)
    class RandomPixelWriter(CompressedPixelWriter):

    def writePixels(self):
    # Bad practice: using globals
    # - BLOCK_W, BLOCK_H, IMAGE_W, IMAGE_H (sort of OK)
    # - bitsPerPixel
    # - imageFilter

    if BLOCK_H > 1:
    repeatPrior = bytearray(1 + bitsPerPixel * IMAGE_W * BLOCK_W)
    repeatPrior[0] = 2 # Up filter
    #repeatPrior *= (BLOCK_H - 1)
    repeatPrior = bytes(repeatPrior)

    for y in range(IMAGE_H):
    # Write scanline
    if BLOCK_W > 1:
    self.write(b"\x01") # Sub
    #prev = bytearray(bitsPerPixel)
    for x in range(IMAGE_W):
    # There is no need to subtract from prev,
    # because random differences are still random.
    self.write(imageFilter(urandom(bitsPerPixel)))
    self.writez(bitsPerPixel * (BLOCK_W - 1))
    else:
    self.write(b"\x00") # no PNG filter
    self.write(imageFilter(urandom(bitsPerPixel * IMAGE_W)))

    # Repeat previous scanline, at least one time, if needed
    for i in range(1, BLOCK_H):
    self.write(repeatPrior)

    with open(OUTPUT_FILE, "wb") as f:
    # Signature
    @@ -111,17 +147,19 @@ def imageFilter(b):
    + B(filtermethod) \
    + B(interlaced)

    f.write(I4(len(IHDR) - 4))
    f.write(I4(len(IHDR) - 4)) # 13
    f.write(IHDR)
    f.write(I4(zlib.crc32(IHDR)))
    # IDAT
    compressor = zlib.compressobj(9) # max compression
    IDAT = b"IDAT" + \
    compressor.compress(pixels) + \
    compressor.flush()
    f.write(I4(len(IDAT) - 4))
    f.write(IDAT)
    f.write(I4(zlib.crc32(IDAT)))
    IDAT_len_offset = f.tell() # 33
    f.write(b"\0\0\0\0IDAT")
    pWriter = RandomPixelWriter(f.write)
    pWriter.finalize()
    f.write(I4(pWriter.crc32))
    # Fix length
    f.seek(IDAT_len_offset)
    f.write(I4(pWriter.length))
    f.seek(0, 2) # to end
    # IEND
    # 0x00000000 + "IEND" + CRC32("IEND")
    f.write(b"\0\0\0\0IEND\xae\x42\x60\x82")
  10. theonlypwner revised this gist Feb 22, 2016. 1 changed file with 1 addition and 1 deletion.
    2 changes: 1 addition & 1 deletion randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -78,7 +78,7 @@ def imageFilter(b):
    if BLOCK_W > 1:
    repeatLeft = bytearray(bitsPerPixel * (BLOCK_W - 1))

    for y in range(IMAGE_W):
    for y in range(IMAGE_H):
    # Write scanline
    if BLOCK_W > 1:
    pixels.append(1) # Sub
  11. theonlypwner revised this gist Feb 22, 2016. 1 changed file with 5 additions and 4 deletions.
    9 changes: 5 additions & 4 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -68,12 +68,13 @@ def imageFilter(b):
    BLOCK_W *= -DEPTH
    else:
    bitsPerPixel = DEPTH
    imageFilter = lambda b: bytes(b)
    imageFilter = bytes

    pixels = bytearray()
    if BLOCK_H > 1:
    repeatPrior = bytearray(1 + bitsPerPixel * IMAGE_W * BLOCK_W)
    repeatPrior[0] = 2 # Up filter
    repeatPrior *= (BLOCK_H - 1)
    if BLOCK_W > 1:
    repeatLeft = bytearray(bitsPerPixel * (BLOCK_W - 1))

    @@ -83,16 +84,16 @@ def imageFilter(b):
    pixels.append(1) # Sub
    #prev = bytearray(bitsPerPixel)
    for x in range(IMAGE_W):
    # We don't need to sub from prev
    # There is no need to subtract from prev,
    # because random differences are still random.
    pixels.extend(imageFilter(urandom(bitsPerPixel)))
    pixels.extend(repeatLeft)
    else:
    pixels.append(0) # no PNG filter
    pixels.extend(imageFilter(urandom(bitsPerPixel * IMAGE_W)))

    # Repeat previous scanline when needed
    for i in range(1, BLOCK_H):
    # Repeat previous scanline, at least one time, if needed
    if BLOCK_H > 1:
    pixels.extend(repeatPrior)

    pixels = bytes(pixels)
  12. theonlypwner revised this gist Feb 22, 2016. 1 changed file with 23 additions and 8 deletions.
    31 changes: 23 additions & 8 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -68,18 +68,33 @@ def imageFilter(b):
    BLOCK_W *= -DEPTH
    else:
    bitsPerPixel = DEPTH
    imageFilter = lambda x: x
    imageFilter = lambda b: bytes(b)

    pixels = bytearray()
    if BLOCK_H > 1:
    repeatPrior = bytearray(1 + bitsPerPixel * IMAGE_W * BLOCK_W)
    repeatPrior[0] = 2 # Up filter
    if BLOCK_W > 1:
    repeatLeft = bytearray(bitsPerPixel * (BLOCK_W - 1))

    for y in range(IMAGE_W):
    row = bytearray()
    row.append(0) # no PNG filter
    if BLOCK_W == 1:
    row.extend(imageFilter(urandom(bitsPerPixel * IMAGE_W)))
    else:
    # Write scanline
    if BLOCK_W > 1:
    pixels.append(1) # Sub
    #prev = bytearray(bitsPerPixel)
    for x in range(IMAGE_W):
    row.extend(imageFilter(urandom(bitsPerPixel)) * BLOCK_W)
    pixels.extend(row * BLOCK_H)
    # We don't need to sub from prev
    # because random differences are still random.
    pixels.extend(imageFilter(urandom(bitsPerPixel)))
    pixels.extend(repeatLeft)
    else:
    pixels.append(0) # no PNG filter
    pixels.extend(imageFilter(urandom(bitsPerPixel * IMAGE_W)))

    # Repeat previous scanline when needed
    for i in range(1, BLOCK_H):
    pixels.extend(repeatPrior)

    pixels = bytes(pixels)

    with open(OUTPUT_FILE, "wb") as f:
  13. theonlypwner created this gist Feb 21, 2016.
    114 changes: 114 additions & 0 deletions randompng.py
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,114 @@
    #!/usr/bin/env python
    # Random PNG generator
    __copyright__ = "Copyright (C) 2016 Victor Zheng"
    __licence__ = "GNU GPL v3"

    # This program is free software: you can redistribute it and/or modify
    # it under the terms of the GNU General Public License as published by
    # the Free Software Foundation, either version 3 of the License, or
    # (at your option) any later version.

    # This program is distributed in the hope that it will be useful,
    # but WITHOUT ANY WARRANTY; without even the implied warranty of
    # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    # GNU General Public License for more details.

    # You should have received a copy of the GNU General Public License
    # along with this program. If not, see <http://www.gnu.org/licenses/>.

    # Settings

    OUTPUT_FILE = "r.png" # Do I really need to explain this?
    BLOCK_W, BLOCK_H = 1, 1 # block size [pixels]
    IMAGE_W, IMAGE_H = 1920, 1080 # image size [blocks]
    DEPTH = 3
    # Color depth [bytes/pixel]
    # 1 Grayscale
    # 3 RGB
    # 4 RGBA
    # -1 Black and White
    # -3 Black and White (as RGB)

    # Script
    from os import urandom
    import struct
    import zlib

    def B(x):
    return struct.pack(">B", x & 0xFF)

    def I4(x):
    return struct.pack(">I", x & 0xFFFFFFFF)

    def rPNG():
    global BLOCK_W

    width = IMAGE_W * BLOCK_W
    height = IMAGE_H * BLOCK_H
    bitdepth = 8 # [bit/sample]
    if DEPTH == 1 or DEPTH == -1:
    colortype = 0
    elif DEPTH == 3 or DEPTH == -3:
    colortype = 2
    elif DEPTH == 4:
    colortype = 6
    else:
    raise NotImplementedError("Unsupported color depth " + DEPTH)
    compresstype = 0 # DEFLATE (only supported method)
    filtermethod = 0 # adaptive (only supported method)
    interlaced = 0 # no

    if DEPTH < 1:
    bitsPerPixel = 1
    def imageFilter(b):
    b = bytearray(b)
    for i in range(len(b)):
    b[i] = -(b[i] & 0x1) & 0xFF
    return bytes(b)
    BLOCK_W *= -DEPTH
    else:
    bitsPerPixel = DEPTH
    imageFilter = lambda x: x

    pixels = bytearray()
    for y in range(IMAGE_W):
    row = bytearray()
    row.append(0) # no PNG filter
    if BLOCK_W == 1:
    row.extend(imageFilter(urandom(bitsPerPixel * IMAGE_W)))
    else:
    for x in range(IMAGE_W):
    row.extend(imageFilter(urandom(bitsPerPixel)) * BLOCK_W)
    pixels.extend(row * BLOCK_H)
    pixels = bytes(pixels)

    with open(OUTPUT_FILE, "wb") as f:
    # Signature
    f.write(b"\x89PNG\r\n\x1A\n")
    # IHDR
    IHDR = b"IHDR" \
    + I4(width) \
    + I4(height) \
    + B(bitdepth) \
    + B(colortype) \
    + B(compresstype) \
    + B(filtermethod) \
    + B(interlaced)

    f.write(I4(len(IHDR) - 4))
    f.write(IHDR)
    f.write(I4(zlib.crc32(IHDR)))
    # IDAT
    compressor = zlib.compressobj(9) # max compression
    IDAT = b"IDAT" + \
    compressor.compress(pixels) + \
    compressor.flush()
    f.write(I4(len(IDAT) - 4))
    f.write(IDAT)
    f.write(I4(zlib.crc32(IDAT)))
    # IEND
    # 0x00000000 + "IEND" + CRC32("IEND")
    f.write(b"\0\0\0\0IEND\xae\x42\x60\x82")

    if __name__ == '__main__':
    rPNG()