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JPEG image compression FAQ, part 1/2
Section - [2] Why use JPEG?

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There are two good reasons: to make your image files smaller, and to store
24-bit-per-pixel color data instead of 8-bit-per-pixel data.

Making image files smaller is a win for transmitting files across networks
and for archiving libraries of images.  Being able to compress a 2 Mbyte
full-color file down to, say, 100 Kbytes makes a big difference in disk
space and transmission time!  And JPEG can easily provide 20:1 compression
of full-color data.  If you are comparing GIF and JPEG, the size ratio is
usually more like 4:1 (see "[4] How well does JPEG compress images?").

Now, it takes longer to decode and view a JPEG image than to view an image
of a simpler format such as GIF.  Thus using JPEG is essentially a
time/space tradeoff: you give up some time in order to store or transmit an
image more cheaply.  But it's worth noting that when network transmission is
involved, the time savings from transferring a shorter file can be greater
than the time needed to decompress the file.

The second fundamental advantage of JPEG is that it stores full color
information: 24 bits/pixel (16 million colors).  GIF, the other image format
widely used on the net, can only store 8 bits/pixel (256 or fewer colors).
GIF is reasonably well matched to inexpensive computer displays --- most
run-of-the-mill PCs can't display more than 256 distinct colors at once.
But full-color hardware is getting cheaper all the time, and JPEG photos
look *much* better than GIFs on such hardware.  Within a couple of years,
GIF will probably seem as obsolete as black-and-white MacPaint format does
today.  Furthermore, JPEG is far more useful than GIF for exchanging images
among people with widely varying display hardware, because it avoids
prejudging how many colors to use (see "[8] What is color quantization?").
Hence JPEG is considerably more appropriate than GIF for use as a Usenet
and World Wide Web standard photo format.

A lot of people are scared off by the term "lossy compression".  But when
it comes to representing real-world scenes, *no* digital image format can
retain all the information that impinges on your eyeball.  By comparison
with the real-world scene, JPEG loses far less information than GIF.
The real disadvantage of lossy compression is that if you repeatedly
compress and decompress an image, you lose a little more quality each time
(see "[10] Does loss accumulate with repeated compression/decompression?").
This is a serious objection for some applications but matters not at all
for many others.

User Contributions:

Report this comment as inappropriate
Nov 11, 2018 @ 11:11 am
Artikel ini menjawab Pertanyaan yang Sering Diajukan tentang kompresi gambar JPEG.
Ini adalah bagian 1, yang meliputi pertanyaan umum dan jawaban tentang JPEG. Bagian 2
memberikan petunjuk khusus sistem dan rekomendasi program. Seperti biasa,
saran untuk peningkatan FAQ ini disambut baik.

Baru sejak versi 14 Maret 1999:
* Memperluas item 10 untuk mendiskusikan rotasi tanpa loss dan pemangkasan JPEG.

Artikel ini mencakup bagian-bagian berikut:

Pertanyaan dasar:

[1] Apa itu JPEG?
[2] Mengapa menggunakan JPEG?
[3] Kapan saya harus menggunakan JPEG, dan kapan saya harus tetap menggunakan GIF?
[4] Seberapa baik gambar kompresi JPEG?
[5] Pengaturan "kualitas" apa yang bagus untuk JPEG?
[6] Di mana saya bisa mendapatkan perangkat lunak JPEG?
[7] Bagaimana cara melihat gambar JPEG yang diposkan di Usenet?

Pertanyaan lanjutan lainnya:

[8] Apa itu kuantisasi warna?
[9] Apa beberapa aturan praktis untuk mengkonversi gambar GIF ke JPEG?
[10] Apakah kehilangan terakumulasi dengan kompresi / dekompresi berulang?
[11] Apa itu JPEG progresif?
[12] Dapatkah saya membuat JPEG transparan?
[13] Apakah tidak ada JPEG lossless?
[14] Mengapa semua argumen tentang format file?
[15] Bagaimana saya mengenali format file yang saya miliki, dan apa yang harus saya lakukan?
[16] Masalah kompatibilitas umum apa saja yang ada di sana?
[17] Bagaimana cara kerja JPEG?
[18] Bagaimana dengan pengkodean aritmatika?
[19] Mungkinkah FPU mempercepat JPEG? Bagaimana dengan chip DSP?
[20] Apakah tidak ada standar M-JPEG untuk film?
[21] Bagaimana jika saya membutuhkan lebih dari 8-bit presisi?
[22] Bagaimana program saya mengekstrak dimensi gambar dari file JPEG?


[23] Di mana saya bisa belajar tentang menggunakan gambar di World Wide Web?
[24] Di mana daftar FAQ diarsipkan?

Artikel ini dan rekannya diposting setiap 2 minggu. Jika Anda tidak dapat menemukannya
Bagian 2, Anda bisa mendapatkannya dari arsip di
(lihat "[24] Di mana daftar FAQ diarsipkan?"). Bagian 2 sangat sering berubah;
dapatkan salinan baru jika yang Anda baca berusia lebih dari beberapa bulan.

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Top Document: JPEG image compression FAQ, part 1/2
Previous Document: [1] What is JPEG?
Next Document: [3] When should I use JPEG, and when should I stick with GIF?

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Last Update March 27 2014 @ 02:11 PM