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Topicm809bfa924eda28cf_1528449000663_0Topic

Saving images in various image file formats

Levelm809bfa924eda28cf_1528449084556_0Level

Second

Core curriculumm809bfa924eda28cf_1528449076687_0Core curriculum

Grade IV - VI

II. Programming and solving problems by using the computer and other digital devices. The student:

3) develops and presents solutions to problems by using basic applications (a text and image editor, a spreadsheet, a programme for creating a multimedia presentation) on the computer or in a cloud to demonstrate the following skills:
a) creating illustrations in an imageimageimage editor: drawing with selected tools, transforming images, adding text to images.

Timingm809bfa924eda28cf_1528449068082_0Timing

45 minutes

General objectivem809bfa924eda28cf_1528449523725_0General objective

The elements of computer graphics.

Specific objectivesm809bfa924eda28cf_1528449552113_0Specific objectives

1. Adjusting the image file formatfile formatfile format to the needs of the user.

2. Saving images in various imageimageimage file formats.

3. Identifying the advantages and disadvantages of the basic image file formats.

Learning outcomesm809bfa924eda28cf_1528450430307_0Learning outcomes

The student:

- adjusts the image file format to his or her needs,

- saves images in various image file formats.

Methodsm809bfa924eda28cf_1528449534267_0Methods

1. Flipped classroom.

2. Learning through observation.

Forms of workm809bfa924eda28cf_1528449514617_0Forms of work

1. Individual work.

2. Class work.

LESSON STAGES

Introductionm809bfa924eda28cf_1528450127855_0Introduction

Before the lesson the students have learnt the information about imageimageimage filename extensions and what they differ in. The teacher initiates a short discussion during which the students answer the questions:

- What are image 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?

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

- the quality and size of the image 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).

Procedurem809bfa924eda28cf_1528446435040_0Procedure

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.A raster 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.m809bfa924eda28cf_1527752256679_0A 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.A raster 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

Download any imageimageimage 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 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 formatfile formatfile format is determined by the following factors:

- the purpose of the image,
- its size,
- its quality,
- the available disc space.

[Illustration 1]

BMP – 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 imageimageimage 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.

[Interactive graphics]

The size of raster image 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 compression is a type of data compression that does not ensure that the reconstructed information will be identical to the original. Lossless compression is a type of data compression that allows the original data to be perfectly reconstructed from the compressed data.m809bfa924eda28cf_1527752263647_0The size of raster image 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 compression is a type of data compression that does not ensure that the reconstructed information will be identical to the original. Lossless compression is a type of data compression that allows the original data to be perfectly reconstructed from the compressed data.

Task 2

In any imageimageimage 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 image you have received from your teacher.

Lesson summarym809bfa924eda28cf_1528450119332_0Lesson summary

When you select the image file formatfile formatfile 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.

The most popular imageimageimage file formats are:

- BMP,
- JPG,
- GIF,
- TIFF.

Selected words and expressions used in the lesson plan

bitmapbitmapbitmap

file formatfile formatfile format

imageimageimage

lossless compressionlossless compressionlossless compression

lossy compressionlossy compressionlossy compression

raster graphicsraster graphicsraster graphics

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image1
image

obraz

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wymowa w języku angielskim: image
file format1
file format

format pliku

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wymowa w języku angielskim: file format
bitmap1
bitmap

bitmapa

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wymowa w języku angielskim: bitmap
lossy compression1
lossy compression

kompresja stratna

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wymowa w języku angielskim: lossy compression
lossless compression1
lossless compression

kompresja bezstratna

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wymowa w języku angielskim: lossless compression
raster graphics1
raster graphics

grafika rastrowa

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wymowa w języku angielskim: raster graphics
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