[feat] new pngchunk encode/decoderr

2024-01-03 04:13:19 +09:00
parent 239d819383
commit a8e50dcd77
10 changed files with 196 additions and 24 deletions
--- a/src/ts/pngChunk.ts
+++ b/src/ts/pngChunk.ts
@@ -0,0 +1,144 @@
+import { Buffer } from 'buffer';
+import crc32 from 'crc/crc32';
+import type { LocalWriter } from './storage/globalApi';
+
+export const PngChunk = {
+    read: (data:Uint8Array, chunkName:string[], arg:{checkCrc?:boolean} = {}) => {
+        let pos = 8
+        let chunks:{[key:string]:string} = {}
+        while(pos < data.length){
+            const len = data[pos] * 0x1000000 + data[pos+1] * 0x10000 + data[pos+2] * 0x100 + data[pos+3]
+            const type = data.slice(pos+4,pos+8)
+            const typeString = new TextDecoder().decode(type)
+            console.log(typeString, len)
+            if(arg.checkCrc){
+                const crc = data[pos+8+len] * 0x1000000 + data[pos+9+len] * 0x10000 + data[pos+10+len] * 0x100 + data[pos+11+len]
+                const crcCheck = crc32(data.slice(pos+4,pos+8+len))
+                if(crc !== crcCheck){
+                    throw new Error('crc check failed')
+                }
+            }
+            if(typeString === 'IEND'){
+                break
+            }
+            if(typeString === 'tEXt'){
+                const chunkData = data.slice(pos+8,pos+8+len)
+                let key=''
+                let value=''
+                for(let i=0;i<10;i++){
+                    if(chunkData[i] === 0){
+                        key = new TextDecoder().decode(chunkData.slice(0,i))
+                        value = new TextDecoder().decode(chunkData.slice(i))
+                        break
+                    }
+                }
+                if(chunkName.includes(key)){
+                    chunks[key] = value
+                }
+            }
+            pos += 12 + len
+        }
+        return chunks
+    },
+    
+    trim: (data:Uint8Array) => {
+        let pos = 8
+        let newData:Uint8Array[] = []
+        while(pos < data.length){
+            const len = data[pos] * 0x1000000 + data[pos+1] * 0x10000 + data[pos+2] * 0x100 + data[pos+3]
+            const type = data.slice(pos+4,pos+8)
+            const typeString = new TextDecoder().decode(type)
+            if(typeString === 'IEND'){
+                newData.push(data.slice(pos,pos+12+len))
+                break
+            }
+            if(typeString === 'tEXt'){
+                pos += 12 + len
+            }
+            else{
+                newData.push(data.slice(pos,pos+12+len))
+                pos += 12 + len
+            }
+        }
+        newData.push(data.slice(pos))
+        return Buffer.concat(newData)
+    },
+
+    write: async (data:Uint8Array, chunks:{[key:string]:string}, options:{writer?:LocalWriter} = {}):Promise<void | Buffer> => {
+        let pos = 8
+        let newData:Uint8Array[] = []
+
+        async function pushData(data:Uint8Array){
+            if(options.writer){
+                await options.writer.write(data)
+            }
+            else{
+                newData.push(data)
+            }
+        }
+
+        await pushData(data.slice(0,8))
+
+        while(pos < data.length){
+            const len = data[pos] * 0x1000000 + data[pos+1] * 0x10000 + data[pos+2] * 0x100 + data[pos+3]
+            const type = data.slice(pos+4,pos+8)
+            const typeString = new TextDecoder().decode(type)
+            if(typeString === 'IEND'){
+                break
+            }
+            if(typeString === 'tEXt'){
+                pos += 12 + len
+            }
+            else{
+                await pushData(data.slice(pos,pos+12+len))
+                pos += 12 + len
+            }
+        }
+        for(const key in chunks){
+            const keyData = new TextEncoder().encode(key)
+            const value = Buffer.from(chunks[key])
+            const lenNum = value.byteLength + keyData.byteLength + 1
+            //idk, but uint32array is not working
+            const length = new Uint8Array([
+                lenNum / 0x1000000 % 0x100,
+                lenNum / 0x10000 % 0x100,
+                lenNum / 0x100 % 0x100,
+                lenNum % 0x100
+            ])
+            const type = new TextEncoder().encode('tEXt')
+            await pushData(length)
+            await pushData(type)
+            await pushData(keyData)
+            await pushData(new Uint8Array([0]))
+            await pushData(value)
+            const crc = crc32(Buffer.concat([type,keyData,new Uint8Array([0]),value]))
+            await pushData(new Uint8Array([
+                crc / 0x1000000 % 0x100,
+                crc / 0x10000 % 0x100,
+                crc / 0x100 % 0x100,
+                crc % 0x100
+            ]))
+        }
+        //create IEND chunk
+        {
+            const length = new Uint8Array((new Uint32Array([0])).buffer)
+            const type = new TextEncoder().encode('IEND')
+            await pushData(length)
+            await pushData(type)
+            const crc = crc32(type)
+            await pushData(new Uint8Array([
+                crc / 0x1000000 % 0x100,
+                crc / 0x10000 % 0x100,
+                crc / 0x100 % 0x100,
+                crc % 0x100
+            ]))
+        }
+
+        if(options.writer){
+            await options.writer.close()
+        }
+        else{
+            return Buffer.concat(newData)
+        }
+    },
+}