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ipf codec mostly works except no dithering

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minjaesong
2022-05-01 18:08:21 +09:00
parent 37d6f76a5f
commit 14b624fb08
2 changed files with 57 additions and 36 deletions
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24
assets/disk0/encodeipf.js
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@@ -105,7 +105,8 @@ let writeCount = 0
let writeBuf = sys.malloc(blockSize * ((hasAlpha) ? 20 : 12))
function chromaToFourBits(f) {
return Math.round((f * 7.5) + 7.5)
let r = Math.round(f * 8) + 7
return (r < 0) ? 0 : (r > 15) ? 15 : r
}
for (let blockY = 0; blockY < Math.ceil(imgh / 4.0); blockY++) {
@@ -124,6 +125,7 @@ for (let blockX = 0; blockX < Math.ceil(imgw / 4.0); blockX++) {
let ox = blockX * 4 + px
let oy = blockY * 4 + py
let offset = channels * (oy * imgw + ox)
let r = sys.peek(imageData + offset) / 255.0
let g = sys.peek(imageData + offset+1) / 255.0
let b = sys.peek(imageData + offset+2) / 255.0
@@ -142,14 +144,14 @@ for (let blockX = 0; blockX < Math.ceil(imgw / 4.0); blockX++) {
}}
// subsample by averaging
let cos1 = chromaToFourBits((cos[0]+cos[1]+cos[4]+cos[5]) / 8.0)
let cos2 = chromaToFourBits((cos[2]+cos[3]+cos[6]+cos[7]) / 8.0)
let cos3 = chromaToFourBits((cos[8]+cos[9]+cos[12]+cos[13]) / 8.0)
let cos4 = chromaToFourBits((cos[10]+cos[11]+cos[14]+cos[15]) / 8.0)
let cgs1 = chromaToFourBits((cgs[0]+cgs[1]+cgs[4]+cgs[5]) / 8.0)
let cgs2 = chromaToFourBits((cgs[2]+cgs[3]+cgs[6]+cgs[7]) / 8.0)
let cgs3 = chromaToFourBits((cgs[8]+cgs[9]+cgs[12]+cgs[13]) / 8.0)
let cgs4 = chromaToFourBits((cgs[10]+cgs[11]+cgs[14]+cgs[15]) / 8.0)
let cos1 = chromaToFourBits((cos[0]+cos[1]+cos[4]+cos[5]) / 4.0)
let cos2 = chromaToFourBits((cos[2]+cos[3]+cos[6]+cos[7]) / 4.0)
let cos3 = chromaToFourBits((cos[8]+cos[9]+cos[12]+cos[13]) / 4.0)
let cos4 = chromaToFourBits((cos[10]+cos[11]+cos[14]+cos[15]) / 4.0)
let cgs1 = chromaToFourBits((cgs[0]+cgs[1]+cgs[4]+cgs[5]) / 4.0)
let cgs2 = chromaToFourBits((cgs[2]+cgs[3]+cgs[6]+cgs[7]) / 4.0)
let cgs3 = chromaToFourBits((cgs[8]+cgs[9]+cgs[12]+cgs[13]) / 4.0)
let cgs4 = chromaToFourBits((cgs[10]+cgs[11]+cgs[14]+cgs[15]) / 4.0)
// append encoded blocks to the file
let outBlock = writeBuf + writeCount
@@ -185,8 +187,8 @@ for (let blockX = 0; blockX < Math.ceil(imgw / 4.0); blockX++) {
// write header to the output file
let headerBytes = [
0x1F, 0x54, 0x53, 0x56, 0x4D, 0x69, 0x50, 0x46, // magic
imgw & 255, (imgw >> 8) & 255, // width
imgh & 255, (imgh >> 8) & 255, // height
imgw & 255, (imgw >>> 8) & 255, // width
imgh & 255, (imgh >>> 8) & 255, // height
((hasAlpha) ? 1 : 0), 0x00, // has alpha
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 // reserved
]