How to Work with Raster Images in LusoCAD

What is a Raster Image in CAD?

A raster image in CAD (Computer-Aided Design) is a digital image made up of a grid of pixels, where each pixel contains a specific colour value. Unlike vector objects, raster images do not possess geometric information.

Características das Imagens Raster

Pixel-based

As imagens raster são constituídas por pequenos quadrados denominados píxeis. pixels. Together, these pixels form the complete image.

Dependents of the Resolution

The quality of a raster image depends on its resolution, usually measured in pixels per inch (PPI). Higher resolution offers greater detail but increases file size and can affect performance.

Common File Formats

The most used raster formats in LusoCAD include:

• JPG / JPEG
• PNG
• Loss-making
• TIFF

These formats are ideal for photographs, scans, and visually complex images.

Using Raster Images in LusoCAD

Background References and Textures

Raster images can be attached as backgrounds or textures, providing visual context to the project.

Import of Scanned Drawings

Digitalised plans, manual sketches or documents can be imported and used as a reference for tracing or aligning entities.

Limitations

Raster images lose quality when enlarged and can become pixelated. For this reason, they are not suitable for designs that require frequent resizing or precise editing, unlike vector objects.

How to Attach Raster Images in LusoCAD

Utilise the command IMAGEATTACH to attach raster images (bi-level, 8-bit grayscale, 8-bit color, or 24-bit color) to the drawing. After attaching, the same image can be inserted multiple times, similar to a block.

It is also possible:

• Crop images
• Adjust brightness, contrast, fade and transparency

Steps for Attaching a Raster Image

1. In the main menu, select Insert > Raster Image Reference
2. Locate the image file and click Open
3. In the dialog box Picture:
   • Active Specify on screen for the Insertion point and Scale
   • Define the angle of Rotation, if necessary
4. Click on OK
5. Specify the insertion point in the drawing
6. Specify the scale factor

How to Scale Raster Images

It is possible to define the scale factor directly in the dialog box Picture.
If no scale is specified, the image is attached with its original dimensions.

• Scale factors are unitless by default
• The image is scaled proportionally according to the factor entered

How to Detach Raster Images

If a raster image is no longer needed, it can be removed from the drawing.

When removing an image:

• All instances, links and definitions are purged from the drawing
• The original image file on disk it is not affected

Presentation of Outlines (IMAGEFRAME Command)

It is possible to activate or deactivate image outlines in the current view.

Values

• 1 – Display and print the image outlines
• 0 Hide contours on screen and print

To activate or deactivate outlines via the menu:

1. Select Modify > Object > Image > Outline
2. Choose one of the following options:
   • Introduction 1 to show the outlines
   • Introduction 0 to hide the outlines

How to Crop Raster Images

Raster images can be cropped with rectangular or polygonal boundaries.

Steps to Crop an Image

1. Select Modify > Crop > Image or write CLIP
2. Select the image to crop
3. Introduction N New limit

Rectangular crop

• Define the first canto
• Opposite corner
• Only the area inside the rectangle remains visible

Polygonal Clipping

• Indicate the points of the polygon
• First Enter To conclude
• Only the area inside the polygon remains visible

Adjust Brightness, Contrast and Fade

Utilise the command Image Adjust to control:

• Shine
• Contrast
• Fading

These adjustments affect only the display and printing.
The original image file and other instances of the image are not changed.

Improving Performance in Raster Image Viewing

LusoCAD allows control of the display quality of raster images to improve performance.

• High Quality - Better image definition, slower visualisation
• Draft Quality – Faster viewing with less detail

The use of the mode Draft can significantly improve performance when working with large-dimension or a large number of raster images.