Aktualności

Kształcenie na odległość

Programy nauczania i scenariusze zajęć do kształcenia ogólnego

Epodręczniki PO KL

Katalog Zasobów Dodatkowych

Gra edukacyjna „Godność, wolność i niepodległość”

Materiały partnerów


Filmy instruktażowe i instrukcje

Wróć do informacji o e-podręczniku Udostępnij materiał Wydrukuj
RFNXVfwQQPS4J

Saving images in various image file formats

Source: licencja: CC 0.

Zapisywanie obrazu w różnych formatach graficznych

You will learn
  • image file formats,

  • to save an image in different file formats,

  • how to select the appropriate image file format for its purpose.

RfopjGD24FftM1
nagranie abstraktu
  • What are imageimageimage files used for?

  • Does the file size affect the image quality?

  • Does the purpose of an image influence the choice of its file formatfile formatfile format?

Rmo72EYGBVKuJ1
nagranie abstraktu

The criteria of selecting the image file format are based on:

  • the quality and size of the imageimageimage intended for printing,

  • the available space on a local disc or in a cloud,

  • the speed of opening and saving the image,

  • the purpose of the image (the image intended for placing on a web site).

R16vucApSSmVC1
nagranie abstraktu

A filename extension is a suffix to the name of a computer file following the last occurrence of the dot character that indicates a specific file type. Due to historical reasons (the DOS operating system) filename extensions usually consist of three characters. In Windows, filename extensions are used to assign file types to appropriate programmes that enable editing them.

raster graphicsraster graphicsraster graphics is an image consisting of pixels arranged side by side, which form the grid of coloured points. Such images are also called bitmaps. They are usually created by devices such as a digital camera or scanner.

Task 1
RhDnrk8uKBHR01
nagranie abstraktu

Download any image from the internet. Enlarge it until you will see the separate points of the bitmapbitmapbitmap.

After you have edited your image, it is crucial to select the file formatfile formatfile format in which you will save it. Your choice will affect the quality of the image and the size of the file in which it will be stored. The choice of the file format is determined by the following factors:

  • the purpose of the image,

  • its size,

  • its quality,

  • the available disc space.

R1OmknFgGQBzy
Saving a file in Paint. The selection of the file type.
Source: GroMar, licencja: CC BY 3.0.
ROpC4D9Puy0a61
nagranie abstraktu

BMP is a bitmaps supported by Windows. Their advantages are their simple structure and a common support by the Windows applications, while their disadvantage is the large file size. Bitmaps can support various colour palettes.

JPG is the most popular image file formatfile formatfile format using lossy compressionlossy compressionlossy compression, which can be characterised by the change of the colour value of particular pixels – this effect is not perceptible by human. It is used most of all for web images and by digital cameras. Its huge compression ratio can cause a significant reduction in the file size. Most applications are able to automatically adjust the compression to the visual quality of an imageimageimage.

PNG is a popular image file format supported by all web browsers. It is a non‑patented replacement for GIF. It supports lossless data compression and transparency. This file format is becoming more and more popular.

GIF is a file format supported by all web browsers that is the most suitable for storing images in a few colours. Its own colour palette is reduced to 256 colours, which may affect the quality of an image. GIF files can be animated.

TIFF is universally accepted as a standard of image files among the publishing industry. It enables using lossy and lossless compressionlossless compressionlossless compression. It is not suited to be used on web sites due to its large file size.

RcWs8fSI3fMCF
Ilustracja interaktywna przedstawia różnice w podglądzie powiększonego rysunku wypełnionego koła zapisanego w formatach: JPEG, GIF, PNG. JPEG przedstawia koło z rozmytymi krawędziami, pod kołem widoczne tło. GIF przedstawia koło z ostrymi krawędziami, pod kołem brak widocznego tła. PNG przedstawia koło z rozmytymi krawędziami, pod kołem brak widocznego tła. Na ilustracji widoczne są numery, a na nich podpisy. 1. JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. {audio}, 2. GIF (the Graphics Interchange Format) is a bitmap image format that is commonly used on the World Wide Web due to its wide support and portability. {audio}, 3. PNG (Portable Network Graphics) is a raster graphics file format that supports lossless data compression. {audio}
The types of image files
Source: GroMar, licencja: CC BY 3.0.
RjnZajZETbH4k1
nagranie abstraktu

The size of raster imageimageimage files is positively correlated with the number of pixels in the image and the depth of colours (the number of bits per pixel). Compression is a method of reducing the number of bits needed to express a piece of information. Images can be compressed by using various methods. Lossy compressionlossy compressionLossy compression is a type of data compression that does not ensure that the reconstructed information will be identical to the original. Lossless compressionlossless compressionLossless compression is a type of data compression that allows the original data to be perfectly reconstructed from the compressed data.

Task 2
R1eJxtqMAgLkl1
nagranie abstraktu

In any image editor, open an image and save it in the folder Image under the name imagex, where x is the consecutive number of the file. Select a different file formatfile formatfile format for each file:

  • monochromatic bitmapbitmapbitmap,

  • 16‑colour bitmap,

  • 256‑colour bitmap,

  • 24‑colour bitmap,

  • JPG,

  • GIF,

  • TIFF,

  • PNG.

Create a table in which you will compare in columns the quality of the image and the size of the file in which it is stored. Repeat the task for the imageimageimage you have received from your teacher.

R1Xc1Z8z3lPiY
nagranie abstraktu

When you select the image file format, you must take into account:

  • its purpose (e.g. for placing on a web site, for printing etc.),

  • its file size (the disc space taken up by the file),

  • the quality you want to obtain.

RKkr1LY0zKvHK
nagranie abstraktu

The most popular image file formats are:

  • BMP,

  • JPG,

  • GIF,

  • TIFF.

Exercises

Exercise 1
RARRriQydNtPt
Wersja alternatywna ćwiczenia: Identify true sentences about image file formats. Możliwe odpowiedzi: 1. GIF is a file format of the limited number of colours., 2. TIFF is a file format that ensures high image quality and takes up little disc space., 3. JPG is a file format of lossy compression., 4. TIFF is a file format that is often used for images placed on web sites., 5. BMP is a file format that takes up little disc space., 6. JPG is a file format in which pixel colours may be different from the original image.
zadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 2

On the internet find the information about the RAW image file format. What is it used for the most frequently and why?

Exercise 3

Describe in English the most popular image file formats (BMP, JPG, GIF, TIFF).

Exercise 4
RuK8CI1rYek99
Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. format pliku - file format, 2. grafika rastrowa - raster graphics, 3. obraz - image, 4. bitmapa - bitmap, 5. kompresja bezstratna - lossy compression, 6. kompresja stratna - lossless compression
zadanie
Source: GroMar, licencja: CC BY 3.0.
RwI4rhoTtlNSx1
Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

bitmap
bitmap

bitmapa

R1IvYWtaQc2sG1
wymowa w języku angielskim: bitmap
file format
file format

format pliku

RhXE6gAUDszn51
wymowa w języku angielskim: file format
image
image

obraz

RfZmjiLZDKR321
wymowa w języku angielskim: image
lossless compression
lossless compression

kompresja bezstratna

RqhcYtFcvtFFN1
wymowa w języku angielskim: lossless compression
lossy compression
lossy compression

kompresja stratna

R18khvk75IohF1
wymowa w języku angielskim: lossy compression
raster graphics
raster graphics

grafika rastrowa

R1MGz8mgWju971
wymowa w języku angielskim: raster graphics

Keywords

file formatfile formatfile format

imageimageimage

raster graphicsraster graphicsraster graphics

Zgłoś problem