Smallest image containing one of every RGB color I'm not sure if this kind of golf is allowed, but here it is.
Your objective is to create an image containing one pixel of every possible RGB color. The image with the smallest file size wins.
Rules:

The image must be a PNG.
The image must contain exactly one of every possible RGB color.
Acceptable image dimensions are:

1x16777216
2x8388608
4x4194304
8x2097152
16x1048576
32x524288
64x262144
128x131072
256x65536
512x32768
1024x16384
2048x8192
4096x4096
8192x2048
16384x1024
32768x512
65536x256
131072x128
262144x64
524288x32
1048576x16
2097152x8
4194304x4
8388608x2
16777216x1

Example Image
49683 bytes

Generated by this Python code:

import struct
import zlib

width = 2 ** 16
height = 2 ** 8
bit_depth = 8
color_type = 2
compression_method = 0
filter_method = 0
interlace_method = 0
scanlines = bytes(
    ([1] + (2 ** 8) * ([2, 1, 1] + (2 ** 8 - 1) * [1, 1, 1]))
    + (2 ** 8 - 1) * ([2] + 2 ** 16 * [2, 1, 2])
)

header = struct.pack(
    &quot;!IIBBBBB&quot;,
    width,
    height,
    bit_depth,
    color_type,
    compression_method,
    filter_method,
    interlace_method,
)
compress = zlib.compressobj(level=9, wbits=15, memLevel=9)
compressed = compress.compress(scanlines) + compress.flush()
png = b&quot;\x89PNG\r\n\x1a\n&quot;
for type, data in [(b&quot;IHDR&quot;, header), (b&quot;IDAT&quot;, compressed), (b&quot;IEND&quot;, b&quot;&quot;)]:
    crc = 0xFFFFFFFF
    for b in type + data:
        crc ^= b
        for k in range(8):
            crc = 0xEDB88320 * (crc &amp; 1) ^ crc &gt;&gt; 1
    crc ^= 0xFFFFFFFF
    png += struct.pack(&quot;!I4s&quot;, len(data), type) + data + struct.pack(&quot;!I&quot;, crc)

print(len(png))
with open(&quot;rgb.png&quot;, &quot;wb&quot;) as f:
    f.write(png)

Try it online!
(Note: many PNG readers accept an image missing the IEND chunk, but it is required by the PNG specification so I have included it.)