BMP二進制圖片處理

BMP文件格式詳解（BMP file format）

TypedArray.prototype

JS BMP二進制圖片的處理

bmpDeal(arrybuffer){
   let w = 1280;
   let h = 960;
   let color = 0;
   let size = w * h;
   let allsize = size + 1080;
   let patte = new Array(1024);
   let end = new Array(2);
   let pos = 0;
   let idx = 0;
   let line = 0;
   let head = [
     0x42, 0x4d, 0x30, 0x0C, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x36, 0x04, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00, 0xF5, 0x00,
     0x00, 0x00, 0x46, 0x00, 0x00, 0x00, 0x01, 0x00, 0x08, 0x00,
     0x00, 0x00, 0x00, 0x00, 0xF8, 0x0b, 0x01, 0x00, 0x12, 0x0b,
     0x00, 0x00, 0x12, 0x0b, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00
   ];
   //位圖信息頭處理
   head[2] = allsize & 0xFF;
   head[3] = (allsize >> 8) & 0xFF;
   head[4] = (allsize >> 16) & 0xFF;
   head[5] = (allsize >> 24) & 0xFF;

   head[18] = w & 0xFF;
   head[19] = (w >> 8) & 0xFF;
   head[20] = (w >> 16) & 0xFF;
   head[21] = (w >> 24) & 0xFF;

   head[22] = h & 0xFF;
   head[23] = (h >> 8) & 0xFF;
   head[24] = (h >> 16) & 0xFF;
   head[25] = (h >> 24) & 0xFF;

   allsize -= 1078;
   head[34] = allsize & 0xFF;
   head[35] = (allsize >> 8) & 0xFF;
   head[36] = (allsize >> 16) & 0xFF;
   head[37] = (allsize >> 24) & 0xFF;

//調色板處理
   for (idx = 0; idx < 1024; idx += 4){
     patte[pos++] = color;
     patte[pos++] = color;
     patte[pos++] = color;
     patte[pos++] = 0;
     color++;
   }

   allsize += 1078;
   let all_un8 = new Uint8Array(allsize);

   //位圖信息頭
   let head_un8 = new Uint8Array(head);
   for (let i = 0; i < head_un8.length; i++) {
     all_un8[i] = head_un8[i];
   }

   //顏色表
   let patte_un8 =  new Uint8Array(patte);
   for (let i = 0; i < patte_un8.length; i++) {
     all_un8[54 + i] = patte_un8[i];
   }

   //位圖數據
   let rgb_un8 = new Uint8Array(arrybuffer);
   for (let idx = h - 1; idx >= 0; idx--){
     //這裏注意  BMP二進制的處理是逆序行讀的
     let sub_rgb_un8 = rgb_un8.subarray(idx * w, (idx+1)*w);
     for(let i = 0; i < sub_rgb_un8.length; i++){
       all_un8[1078 + line * w + i] = sub_rgb_un8[i]
     }
     line ++
   }
   //尾部處理
   let end_un8 = new Uint8Array(end);
   all_un8[allsize-2] = end_un8[0];
   all_un8[allsize-1] = end_un8[1];

   //也可以通過set方式寫入
   //all_un8.set(new Uint8Array(head));
   //all_un8.set(new Uint8Array(patte),  54);
   //for (let idx = h - 1; idx >= 0; idx--){
   //  all_un8.set(rgb_un8.subarray(idx * w, (idx+1)*w),  1078 + line * w);
   //  line ++
   //}
   //all_un8.set(new Uint8Array(end),allsize-2);

   return all_un8;
 },