GIF Compression Explained ガチョウの写真

GIF Compression Explained

This may not be an exact representation of what goes on in a GIF, but I'm guessing it's close enough for our purposes.

Let's suppose you have a 6x6 gif image made up of 3 colors a,b and c...

Or in terms of a, b and c...

c c c c c c
c b b b b b a = red
c b b b b b b = green
c a a b b b c = blue
c a a b b b
c c c c c c

One way to "describe" this image is

first row c-c-c-c-c-c
second row c-b-b-b-b-b
etc

Each pixel is defined one at a time.

Let's suppose we tried to save a little time though and described it like this...

1:6c
2:c-5b
etc

By attempting to group pixels together you save room. If we had a very large image that started off like this...

first row c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c
second row c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c

A gif might simply say...

1:25c
2:25c

This is gif "compression".

Let's suppose that instead of all c's in those first two rows, there are other colors...

first row c-c-c-c-b-b-b-a-b-b-a-a-a-a-a-c-c-b-b-b-a-b-c-c-c
second row a-a-a-a-b-b-b-a-b-c-c-c-c-c-b-b-b-b-c-c-c-c-c-c-c

This would compress into...

1:4c-3b-a-2b-5a-2c-3b-a-b3c
2:4a-3b-a-b-5c-4b-7c

Now let's suppose instead of 3 colors, we reduced the number of colors to 2. We'll remove a and substitute b instead. If a and b are similar colors, the image quality may not suffer very much at all...

first row c-c-c-c-b-b-b-b-b-b-b-b-b-b-b-c-c-b-b-b-b-b-c-c-c
second row b-b-b-b-b-b-b-b-b-c-c-c-c-c-b-b-b-b-c-c-c-c-c-c-c

This would compress into...

1:4c-11b-2c-5b-3c
2:9b-5c-4b-7c

Compare this to the last example. Do you see how this would translate into a smaller file size?

One of the worst things you can do to a gif is make it speckled...

first row c-b-c-b-c-b-c-b-c-b-c-b-c-b

Because what would that compress into?

1:c-b-c-b-c-b-c-b-c-b-c-b-c-b

You don't save a thing.

So, the whole business of gif compression revolves around one simple idea... reduce the number of colors and/or color changes in the file.

Related articles you may find interesting... GIF or JPG and Image Compression Examples.


ガチョウの写真

canada goose jacket miehet
カナダのガチョウのジャケット
canada gansa EUA
Canada Goose clearance

GIF Compression Explained

This may not be an exact representation of what goes on in a GIF, but I'm guessing it's close enough for our purposes.

Let's suppose you have a 6x6 gif image made up of 3 colors a,b and c...

Or in terms of a, b and c...

c c c c c c
c b b b b b a = red
c b b b b b b = green
c a a b b b c = blue
c a a b b b
c c c c c c

One way to "describe" this image is

first row c-c-c-c-c-c
second row c-b-b-b-b-b
etc

Each pixel is defined one at a time.

Let's suppose we tried to save a little time though and described it like this...

1:6c
2:c-5b
etc

By attempting to group pixels together you save room. If we had a very large image that started off like this...

first row c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c
second row c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c

A gif might simply say...

1:25c
2:25c

This is gif "compression".

Let's suppose that instead of all c's in those first two rows, there are other colors...

first row c-c-c-c-b-b-b-a-b-b-a-a-a-a-a-c-c-b-b-b-a-b-c-c-c
second row a-a-a-a-b-b-b-a-b-c-c-c-c-c-b-b-b-b-c-c-c-c-c-c-c

This would compress into...

1:4c-3b-a-2b-5a-2c-3b-a-b3c
2:4a-3b-a-b-5c-4b-7c

Now let's suppose instead of 3 colors, we reduced the number of colors to 2. We'll remove a and substitute b instead. If a and b are similar colors, the image quality may not suffer very much at all...

first row c-c-c-c-b-b-b-b-b-b-b-b-b-b-b-c-c-b-b-b-b-b-c-c-c
second row b-b-b-b-b-b-b-b-b-c-c-c-c-c-b-b-b-b-c-c-c-c-c-c-c

This would compress into...

1:4c-11b-2c-5b-3c
2:9b-5c-4b-7c

Compare this to the last example. Do you see how this would translate into a smaller file size?

One of the worst things you can do to a gif is make it speckled...

first row c-b-c-b-c-b-c-b-c-b-c-b-c-b

Because what would that compress into?

1:c-b-c-b-c-b-c-b-c-b-c-b-c-b

You don't save a thing.

So, the whole business of gif compression revolves around one simple idea... reduce the number of colors and/or color changes in the file.

Related articles you may find interesting... GIF or JPG and Image Compression Examples.



プライベートモード

人に見られたくない動画ファイルや再生履歴を隠す

プレミアムプランにアップグレードすると、人に見られたくない動画ファイルや再生履歴を隠すことができます。プライベートモードを有効にするには最初にPINコード(パスワード)を設定しますので、あなた以外のアクセスを制御できます。


プライベートモードを利用するメリット

  • PINコード(パスワード)によりアクセスを制御できます
  • ダウンロードしたすべての動画を隠しフォルダへ保存できます
  • 動画ファイルを選択して隠しフォルダへ移動できます
  • 隠しフォルダ内の動画ファイルは、プライベートモードが有効のときだけにライブラリで確認できます
  • プライベートモード終了時に再生履歴は自動削除されます

プレミアム機能を使用するには
プレミアムプランにアップグレード

  • 常に最新のプレミアム機能を使用可能
  • クラウド容量を25GB追加
  • 月額499円(税別)
もっと詳しく

基本機能

  • 動画ダウンロード
  • 変換と転送
  • スマホやタブレットとの
    接続
  • CDへ書き込み
  • 再生
  • 管理
  • 編集(トリミング)
  • 共有

プレミアム機能

  • プライベートモード
    (人に見られたくない動画ファイルや再生履歴を隠す)
  • DVDへ書き込み/高品質CDを作成
  • 高度な再生
  • プレイパック
    (より多くの種類の形式のファイルを再生・変換・編集)
  • ミュージッククリーナー
    (音楽ライブラリを自動整理)
  • ライブラリ保管