lossy image compressor wip

assets/disk0/encodeipf.js

@@ -0,0 +1,149 @@
+/*
+TSVM Interchangeable Picture Format
+
+Image is divided into 4x4 blocks and each block is serialised, then the entire file is gzipped
+
+
+# File Structure
+\x1F T S V M i P F
+[HEADER]
+[Blocks.gz]
+
+- Header
+    uint16 WIDTH
+    uint16 HEIGHT
+    uint16 HAS ALPHA
+    byte[10] RESERVED
+
+- *.gz
+    uint32 UNCOMPRESSED SIZE
+    *      PAYLOAD
+
+- Blocks
+    4x4 pixels are sampled, then divided into YCoCg planes.
+    CoCg planes are "chroma subsampled" by 4:2:0, then quantised to 4 bits (8 bits for CoCg combined)
+    Y plane is quantised to 4 bits
+
+    By doing so, CoCg planes will reduce to 4 pixels
+    For the description of packing, pixels in Y plane will be numbered as:
+        0 1 2 3
+        4 5 6 7
+        8 9 A B
+        C D E F
+
+    Bits are packed like so:
+
+    uint8 [Cg-Top Left | Co-Top Left]
+    uint16 [Y1 | Y0 | Y5 | Y4]
+    uint8 [Cg-Top Right | Co-Top Right]
+    uint16 [Y3 | Y2 | Y7 | Y6]
+    uint8 [Cg-Bottom Left | Co-Bottom Left]
+    uint16 [Y9 | Y8 | YD | YC]
+    uint8 [Cg-Bottom Right | Co-Bottom Right]
+    uint16 [YB | YA | YF | YE]
+    (total: 96 bytes)
+
+    If has alpha, append following bytes for alpha values
+    uint16 [a1 | a0 | a5 | a4]
+    uint16 [a3 | a2 | a7 | a6]
+    uint16 [a9 | a8 | aD | aC]
+    uint16 [aB | aA | aF | aE]
+    (total: 160 bytes)
+
+
+
+ */
+
+if (!exec_args[2]) {
+    printerrln("Usage: entsvmipf input.jpg output.ipf")
+    return 1
+}
+
+let configUseAlpha = true
+
+filesystem.open("A", exec_args[1], "R")
+
+let status = com.getStatusCode(0)
+let infile = undefined
+if (0 != status) return status
+
+// read file
+let fileLen = filesystem.getFileLen("A")
+infile = sys.malloc(fileLen)
+dma.comToRam(0, 0, infile, fileLen)
+
+// decode
+const [imgw, imgh, imageData, channels] = graphics.decodeImage(infile, fileLen) // stored as [R | G | B | (A)]
+let hasAlpha = (4 == channels) && configUseAlpha
+let blockCount = Math.ceil(imgh / 4.0) * Math.ceil(imgw / 4.0)
+let serialisedBlocks = sys.malloc((hasAlpha) ? blockCount * 20 : blockCount * 12)
+let blocksWriteCount = 0
+for (let blockY = 0; blockY < Math.ceil(imgh / 4.0); blockY++) {
+for (let blockX = 0; blockX < Math.ceil(imgw / 4.0); blockx++) {
+    let pixelWordOffset = channels * (blockY * 4) * imgw + (blockX * 4)
+    let ys = Uint8Array(16)
+    let as = Uint8Array(16)
+    let cos = Float32Array(16)
+    let cgs = Float32Array(16)
+    for (let py = 0; py < 4; py++) { for (let px = 0; px < 4; px++) {
+        let offset = imageData + pixelWordOffset + 4 * (px + py * imgw)
+        let r = sys.peek(offset) / 255.0
+        let g = sys.peek(offset+1) / 255.0
+        let b = sys.peek(offset+2) / 255.0
+        let a = (hasAlpha) ? sys.peek(offset+3) / 255.0 : 1.0
+
+        let co = r - b // [-1..1]
+        let tmp = b + co / 2.0
+        let cg = g - tmp // [-1..1]
+        let y = tmp + cg / 2.0 // [0..1]
+
+        let index = py * 4 + px
+        ys[index] = Math.round(y * 15)
+        as[index] = Math.round(a * 15)
+        cos[index] = co
+        cgs[index] = cg
+    }}
+
+    // subsample by averaging
+    cos1 = Math.round((((cos[0]+cos[1]+cos[4]+cos[5]) / 4.0) + 1) * 15)
+    cos2 = Math.round((((cos[2]+cos[3]+cos[6]+cos[7]) / 4.0) + 1) * 15)
+    cos3 = Math.round((((cos[8]+cos[9]+cos[12]+cos[13]) / 4.0) + 1) * 15)
+    cos4 = Math.round((((cos[10]+cos[11]+cos[14]+cos[15]) / 4.0) + 1) * 15)
+    cgs1 = Math.round((((cgs[0]+cgs[1]+cgs[4]+cgs[5]) / 4.0) + 1) * 15)
+    cgs2 = Math.round((((cgs[2]+cgs[3]+cgs[6]+cgs[7]) / 4.0) + 1) * 15)
+    cgs3 = Math.round((((cgs[8]+cgs[9]+cgs[12]+cgs[13]) / 4.0) + 1) * 15)
+    cgs4 = Math.round((((cgs[10]+cgs[11]+cgs[14]+cgs[15]) / 4.0) + 1) * 15)
+
+    // append encoded blocks
+    let outBlock = serialisedBlocks + blocksWriteCount
+
+    sys.poke(outBlock+ 0, (cgs1 << 4) | cos1)
+    sys.poke(outBlock+ 1, (ys[1] << 4) | ys[0])
+    sys.poke(outBlock+ 2, (ys[5] << 4) | ys[4])
+    sys.poke(outBlock+ 3, (cgs2 << 4) | cos2)
+    sys.poke(outBlock+ 4, (ys[3] << 4) | ys[2])
+    sys.poke(outBlock+ 5, (ys[7] << 4) | ys[6])
+    sys.poke(outBlock+ 6, (cgs3 << 4) | cos3)
+    sys.poke(outBlock+ 7, (ys[9] << 4) | ys[8])
+    sys.poke(outBlock+ 8, (ys[13] << 4) | ys[12])
+    sys.poke(outBlock+ 9, (cgs4 << 4) | cos4)
+    sys.poke(outBlock+10, (ys[11] << 4) | ys[10])
+    sys.poke(outBlock+11, (ys[15] << 4) | ys[14])
+
+    if (hasAlpha) {
+        sys.poke(outBlock+12, (as[1] << 4) | as[0])
+        sys.poke(outBlock+13, (as[5] << 4) | as[4])
+        sys.poke(outBlock+14, (as[3] << 4) | as[2])
+        sys.poke(outBlock+15, (as[7] << 4) | as[6])
+        sys.poke(outBlock+16, (as[9] << 4) | as[8])
+        sys.poke(outBlock+17, (as[13] << 4) | as[12])
+        sys.poke(outBlock+18, (as[11] << 4) | as[10])
+        sys.poke(outBlock+19, (as[15] << 4) | as[14])
+
+        blocksWriteCount += 8
+    }
+    blocksWriteCount += 12
+
+}}
+
+// TODO open outfile, write header, write serialisedBlocks.gz