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我一直在摆弄jpeg-js模块和节点JS缓冲区，试图创建一个小的命令行程序来修改已解码的JPEG缓冲区数据，并创建一个X数量的反转扫描线和X数量的正常扫描线保存一个新的JPEG。换句话说，我正在寻找翻转图像的部分，但不是整个图像本身（当然有大量的模块可以做这样的事情，但不是我具体的使用案例）。如何使用jpeg-js模块/节点JS缓冲区反转扫描线？
为了创建反转/正常的线条图案，我一直在逐行阅读/写入，并将该线条的一部分保存到一个变量中，然后从扫描线的末端开始，并逐渐递减4字节（一个RGBA值的分配），直到我在行的开头。程序代码：
'use strict';
const fs = require('fs');
const jpeg = require('jpeg-js');
const getPixels = require('get-pixels');
let a = fs.readFileSync('./IMG_0006_2.jpg');
let d = Buffer.allocUnsafe(a.width * a.height * 4);
let c = jpeg.decode(a);
let val = false; // track whether normal or reversed scanlines
let lineWidth = b.width * 4;
let lineCount = 0;
let track = 0;
let track2 = 0;
let track3 = 0;
let curr, currLine; // storage for writing/reading scnalines, respectively
let limit = {
one: Math.floor(Math.random() * 141),
two: Math.floor(Math.random() * 151),
three: Math.floor(Math.random() * 121)
};
if (limit.one < 30) {
limit.one = 30;
}
if (limit.two < 40) {
limit.two = 40;
}
if (limit.two < 20) {
limit.two = 20;
}
let calc = {};
calc.floor = 0;
calc.ceil = 0 + lineWidth;
d.forEach(function(item, i) {
if (i % lineWidth === 0) {
lineCount++;
/* // alternate scanline type, currently disabled to figure out how to succesfully reverse image
if (lineCount > 1 && lineCount % limit.one === 0) {
// val = !val;
}
*/
if (lineCount === 1) {
val = !val; // setting alt scanline check to true initially
} else if (calc.floor + lineWidth < b.data.length - 1) {
calc.floor += lineWidth;
calc.ceil += lineWidth;
}
currLine = c.data.slice(calc.floor, calc.ceil); // current line
track = val ? lineWidth : 0; // tracking variable for reading from scanline
track2 = val ? 4 : 0; // tracking variable for writing from scanline
}
//check if reversed and writing variable has written 4 bytes for RGBA
//if so, set writing source to 4 bytes at end of line and read from there incrementally
if (val && track2 === 4) {
track2 = 0; // reset writing count
curr = currLine.slice(track - 4, track); // store 4 previous bytes as writing source
if (lineCount === 1 && lineWidth - track < 30) console.log(curr); //debug
} else {
curr = currLine; //set normal scanline
}
d[i] = curr[track2];
// check if there is no match between data source and decoded image
if (d[i] !== curr[track2]) {
if (track3 < 50) {
console.log(i);
}
track3++;
}
track2++; //update tracking variable
track = val ? track - 1 : track + 1; //update tracking variable
});
var rawImageData = {
data: d,
width: b.width,
height: b.height
};
console.log(b.data.length);
console.log('errors\t', track3);
var jpegImageData = jpeg.encode(rawImageData, 100);
fs.writeFile('foo2223.jpg', jpegImageData.data);
唉，我写的反向扫描代码不正确。不幸的是，我只能成功地颠倒我测试图像的红色通道（见左下图），蓝色和绿色通道变成了模糊的模糊。配色方案应该看起来像正确的图像。
我在做什么错在这里？
