2 files changed, 65 insertions(+), 36 deletions(-)

A README.md
M main.go

@@ 0,0 1,39 @@
+# PNG Banger
+
+Hand rolled, artisinal, piece of junk PNG encoder.
+
+Features:
+
+- 🎢 Hand rolled CRC32
+- 🎨 Artisinal Adler32
+- 🖼️  Piece of junk uncompressed zlib/DEFLATE framing
+- ⛳ Adequate, if sub-par, performance
+- 🛏️  Arbitrary limitations due to laziness
+- 🚮 No tests
+- 🍝 Not even useful as copypasta
+
+
+## Whyyy?
+
+I have a very handy piece of Javascript copypasta that encodes BMP files (most
+underrated image format ever, not joking). It's surprisingly useful for adding
+image grinding functionalty to existing code and avoiding grappling with
+shithouse Javascript image libraries when they're not needed.
+
+I wanted to see if a similar thing was viable for encoding basic, no-frills,
+don't-really-care-how-big-it-is PNG files. Looks like it probably isn't. Oh
+well.
+
+
+## Expectation management
+
+This is a tool I hack on for my own amusement in an ad-hoc fashion. *No
+stability guarantees are made*, the code is *not guaranteed to work*, and
+anything may be changed, renamed or removed at any time as I see fit.
+
+If you wish to use any of this, I strongly recommend you copy-paste pieces
+as-needed (including tests and license/attribution) into your own project,
+or fork it for your own purposes.
+
+Bug reports are welcome, feature requests discouraged, and code contributions
+will not be accepted.

@@ 149,10 149,8 @@ func appendZlibFraming(out []byte, data []byte) []byte {
 		var sz16 = uint16(sz) // Encoded size includes the size bytes and mark
 		out = append(out,
 			mark,
-			uint8(sz16),
-			uint8(sz16>>8),
-			uint8(^sz16),
-			uint8(^sz16>>8))
+			uint8(sz16), uint8(sz16>>8),
+			uint8(^sz16), uint8(^sz16>>8))
 		out = append(out, data[:sz]...)
 		data = data[sz:]
 	}


@@ 360,9 358,9 @@ func pngBangPalettedEntangled(img *image.Paletted) []byte {
 
 	var blockSizeIdx = len(out) + 1 // When we write the zlib block size, write it to this index
 	out = append(out,
-		0,    // mark
-		0, 0, // len
-		0, 0, // ^len
+		0x00,       // mark
+		0x00, 0x00, // len
+		0x00, 0x00, // ^len
 	)
 
 	var blockSize int


@@ 372,17 370,15 @@ func pngBangPalettedEntangled(img *image.Paletted) []byte {
 		if blockSize+len(row)+1 > maxFrame {
 			// Don't bother with perfectly stuffed frames, this is simpler.
 			sz16 := uint16(blockSize)
-			out[blockSizeIdx+0] = uint8(sz16)
-			out[blockSizeIdx+1] = uint8(sz16 >> 8)
-			out[blockSizeIdx+2] = uint8(^sz16)
-			out[blockSizeIdx+3] = uint8(^sz16 >> 8)
+			out[blockSizeIdx+0], out[blockSizeIdx+1] = uint8(sz16), uint8(sz16>>8)
+			out[blockSizeIdx+2], out[blockSizeIdx+3] = uint8(^sz16), uint8(^sz16>>8)
 			blockSize = 0
 
 			blockSizeIdx = len(out) + 1
 			out = append(out,
-				0,    // mark
-				0, 0, // len
-				0, 0, // ^len
+				0x00,       // mark
+				0x00, 0x00, // len
+				0x00, 0x00, // ^len
 			)
 		}
 


@@ 396,13 392,11 @@ func pngBangPalettedEntangled(img *image.Paletted) []byte {
 	}
 
 	sz16 := uint16(blockSize)
-	out[blockSizeIdx+0] = uint8(sz16)
-	out[blockSizeIdx+1] = uint8(sz16 >> 8)
-	out[blockSizeIdx+2] = uint8(^sz16)
-	out[blockSizeIdx+3] = uint8(^sz16 >> 8)
+	out[blockSizeIdx+0], out[blockSizeIdx+1] = uint8(sz16), uint8(sz16>>8)
+	out[blockSizeIdx+2], out[blockSizeIdx+3] = uint8(^sz16), uint8(^sz16>>8)
 	out = append(out,
-		1,    // mark
-		0, 0, // len
+		0x01,       // mark
+		0x00, 0x00, // len
 		0xff, 0xff, // ^len
 	)
 


@@ 483,9 477,9 @@ func pngBangTrueEntangled(img *image.NRGBA) []byte {
 
 	var blockSizeIdx = len(out) + 1 // When we write the zlib block size, write it to this index
 	out = append(out,
-		0,    // mark
-		0, 0, // len
-		0, 0, // ^len
+		0x00,       // mark
+		0x00, 0x00, // len
+		0x00, 0x00, // ^len
 	)
 
 	var blockSize int


@@ 496,17 490,15 @@ func pngBangTrueEntangled(img *image.NRGBA) []byte {
 			// FIXME: split rows will be necessary if we want to support rows
 			// greater than 8191px.
 			sz16 := uint16(blockSize)
-			out[blockSizeIdx+0] = uint8(sz16)
-			out[blockSizeIdx+1] = uint8(sz16 >> 8)
-			out[blockSizeIdx+2] = uint8(^sz16)
-			out[blockSizeIdx+3] = uint8(^sz16 >> 8)
+			out[blockSizeIdx+0], out[blockSizeIdx+1] = uint8(sz16), uint8(sz16>>8)
+			out[blockSizeIdx+2], out[blockSizeIdx+3] = uint8(^sz16), uint8(^sz16>>8)
 
 			blockSize = 0
 			blockSizeIdx = len(out) + 1
 			out = append(out,
-				0,    // mark
-				0, 0, // len
-				0, 0, // ^len
+				0x00,       // mark
+				0x00, 0x00, // len
+				0x00, 0x00, // ^len
 			)
 		}
 


@@ 520,13 512,11 @@ func pngBangTrueEntangled(img *image.NRGBA) []byte {
 	}
 
 	sz16 := uint16(blockSize)
-	out[blockSizeIdx+0] = uint8(sz16)
-	out[blockSizeIdx+1] = uint8(sz16 >> 8)
-	out[blockSizeIdx+2] = uint8(^sz16)
-	out[blockSizeIdx+3] = uint8(^sz16 >> 8)
+	out[blockSizeIdx+0], out[blockSizeIdx+1] = uint8(sz16), uint8(sz16>>8)
+	out[blockSizeIdx+2], out[blockSizeIdx+3] = uint8(^sz16), uint8(^sz16>>8)
 	out = append(out,
-		1,    // mark
-		0, 0, // len
+		0x01,       // mark
+		0x00, 0x00, // len
 		0xff, 0xff, // ^len
 	)