• ChaoticNeutralCzech@lemmy.ml
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      11 个月前

      I prefer hexadecimal. The encoded data in its entirety is

      89 50 4E 47 0D 0A 1A 0A 
      00 00 00 0D 49 48 44 52 
      00 00 01 2C 00 00 01 2C 
      08 06 00 00 00 B9 B4 AC 
      33 00 00 01 A4 49 44 41 
      54 78 9C ED DD 41 8E 83 
      40 10 85 E1 7F 7F E4 B2 
      72 25 92 61 64 98 59 26 
      16 49 85 92 61 64 98 59 
      26 16 49 85 92 61 64 98 
      59 26 16 49 85 92 61 64 
      98 59 26 16 49 85 92 61 
      64 98 59 26 16 49 85 92 
      61 64 98 59 26 16 49 85 
      92 61 64 98 59 26 16 49 
      85 92 61 64 98 59 26 16 
      49 85 92 61 64 98 59 26 
      16 49 85 92 61 64 98 59 
      26 16 49 85 92 61 64 98 
      59 26 16 49 85 92 61 64 
      98 59 26 16 49 85 92 61 
      64 98 59 26 16 49 85 92 
      61 64 98 59 26 16 49 85 
      92 61 64 98 59 26 16 49 
      85 92 61 64 98 59 26 16 
      49 85 92 61 64 98 59 26 
      16 49 85 92 61 64 98 59 
      26 16 49 85 92 61 64 98 
      59 26 16 49 85 92 61 64 
      98 59 26 1(abrupt end at 4 bits of last byte)
      

      We can analyze the PNG file header. Surprisingly, some of it makes sense.

      89 50 4E 47 0D 0A 1A 0A //PNG signature (0x89 P N G 0xD 0xA 0x1A 0xA)
      
      00 00 00 0D // Start of chunk with data length 13 bytes
      49 48 44 52 // Type of chunk: IHDR (image header)
      00 00 01 2C // Width: 300 px
      00 00 01 2C // Height: 300 px 
      08 // Bits per color channel: 8 
      06 // Color format: 6 (RGBA)
      00 // Compression method: 0 (DEFLATE)
      00 // Filter method: 0 (Adaptive)
      00 // Interlace method: 0 (None)
      B9 B4 AC 33 // CRC-32 of chunk (invalid, should be 79 7D 8E 75)
      
      00 00 01 A4 // Start of chunk with data length 420 bytes
      49 44 41 54 // Type of chunk: IDAT (image data)
      78 9C ED DD 41 8E 83 40 
      10 85 E1 7F 7F E4 B2 72 25 
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 16 49 85
      92 61 64 98 59 26 1
      // 194.5 of the expected 420 data bytes, invalid when attempting to deflate
      // the deflate algorithm needs a Huffman tree but an unfull one is presented
      

      Credits to the PNG chunk inspector at nayuki.io

      You may try to figure out if the header checksum was stolen from elsewhere and corresponds to another common image size but I cannot be bothered. The data could be subjected to forensic analysis but we only really have 21 unique bytes, the rest is likely nonsense because data encoded by the DEFLATE algorithm is unlikely to be so repetitive. Also, the image in total will likely have just 481 bytes (8+(8+13+4)+(8+420+4)+16), as a less-than-65535-byte IDAT chunk tends to be the last one before a 16-byte trailer. There are very few 300x300 PNGs of such small size we could call memes, most of it will have to be just solid color. Example of a 256x256 map tile you can store in around that size (467 B):
      OSM tile for Crozet Islands at around 1:10 000 000 scale, the archipelago the area of Malta is represented by about 10 white pixels with the exclusive economic zone circles of radius 5 px around the islands
      (And this one is pre-optimized, using an indexed palette of just 13 distinct RGB colors as opposed to the full RGBA gamut!)