This chapter introduces the basic principles of laser engraving and how to simulate grayscale transitions using dynamic laser power and "Dithering" techniques. It also explains that LaserPecker Design Space software supports the use of different dithering algorithms through the "Image Mode" setting to process images with color transitions.
Laser engraving is a processing method that uses a high-density energy laser beam to irradiate the surface of a material, causing it to be instantly heated, melted, vaporized, or ablated, thus achieving the engraving effect. After laser engraving, the background color presented differs from the color of the material surface. This engraving effect is commonly referred to as filled engraving or can be described as a "black-and-white" engraving effect.
However, if the image to be engraved itself contains color or grayscale variations, how can we achieve a color transition effect during engraving?
Laser engraving typically cannot directly produce colored engravings, but we can effectively simulate color depth and transition effects using the following two methods:
- Dynamic Laser Power: The laser power affects the engraving depth. By dynamically adjusting the laser power during the engraving process, the depth of the engraving corresponds to the grayscale values in the image—higher power for darker areas (resulting in deeper engraving) and lower power for lighter areas (resulting in shallower engraving). This creates a natural grayscale transition, similar to mixing black and white pigments in varying proportions to achieve different shades of gray.
- Dithering: This is a technique used to convert the image into a pixelated pattern, with denser dots in darker areas and sparser dots in lighter areas. Even though only black and white dots are used, it can present rich shading and contrast, creating a visual effect similar to color transitions. Laser engraving can use this technique to simulate a grayscale transition effect.
It is worth noting that the LaserPecker Design Space software supports the use of different dithering algorithms through the "Image Mode" setting to process images with color transitions.
1. The Working Principle of Dithering
This chapter introduces the principles of Dithering technology, common Dithering algorithms, and their applicable scenarios. Then concludes with an overview of the Dithering algorithm used in LaserPecker Design Space and the process of implementing this effect.
Dithering is an image processing algorithm that was first applied in the early days of computer graphics display. In the 1980s, many computer screens or printers could only display black and white or a limited range of colors (such as 2, 4, or 16 colors), making it impossible to reproduce the rich colors of real images. Due to the limited number of colors, the image may exhibit noticeable color blocks and banding (known as "color bands"), making it appear unnatural. For example, when a color image is reduced to only black and white, the result would look like the image below.
To solve this problem, the Dithering technique was developed. It works by arranging dots of varying colors (such as black and white dots) in a regular pattern within the image, creating a "blended color" visual effect when viewed from a certain distance. The core idea of Dithering is to simulate grayscale transitions through the arrangement and density variation of the dots, thus achieving a visual color transition effect. The image below demonstrates how Dithering simulates grayscale transitions through changes in dot density.
LaserPecker Design Space offers a variety of dithering effects, referred to as "Image Mode" in the software, including Grayscale, Jarvis, Burkes, Floyd, Stucki, Atkinson, and Sierra, with the default mode set to Stucki.
Below, an image will be used to demonstrate how it looks with different dithering effects. You can click on the image to view a larger version.
Grayscale | |
Grayscale mode transforms an image into various shades of gray, where each pixel represents a different level of darkness, from black to white. The darker the pixel, the deeper the engraving. This method allows for more nuanced shading compared to basic dithering. | |
Jarvis | Burkes |
Jarvis mode is suitable for images that require high color fidelity and detail preservation, especially grayscale images or those with noticeable color transitions. It creates a more natural effect in the gradient areas of the image without producing obvious grid patterns. | Burkes mode provides a balanced trade-off between image fidelity and smooth gradients, avoiding harsh patterns. It is well-suited for images requiring detailed gray scales or those with complex textures and moderate contrast. |
Floyd | Stucki |
Floyd mode works well for images with simpler details or less complex transitions, but it is not ideal for images with a lot of intricate details, as it may create a subtle wavy pattern on the image. | Stucki mode helps preserve image details, reduces blurriness, and restores grayscale transitions more naturally. It avoids color blocks or abrupt changes, making it particularly suitable for processing fine images like photographs, with smoother and more realistic engraving results. |
Atkinson | Sierra |
Atkinson mode is suitable for images that require high contrast and simple structures, particularly simple graphics, black-and-white illustrations, or high-contrast images. It is not well-suited for processing complex color transitions or images with rich details. | Sierra mode is suitable for images that need to retain image details, especially those with high contrast or grayscale images. It may produce visible noise in images with less fine detail. |
2. What Images are Suitable for Dithering
This chapter introduces two common types of images: Bitmap and Vector graphics. It advises that Dithering effects are suitable for bitmaps with rich color or grayscale levels, and also clarifies why black-and-white effects are more appropriate than Dithering for black-and-white images or images with simpler color contrasts.
After understanding the basic principles of the Dithering mode, the next step is to introduce two common types of images: Bitmaps and Vector images.
Bitmaps, also known as raster images, are made up of many individual "pixels", with each pixel representing the color of a specific position in the image. Common bitmap formats include JPG/JPEG, TIF, PNG, and BMP. The LDS PC version supports importing JPG/JPEG, TIF, PNG, and BMP formats, while the mobile version supports importing JPG and PNG formats.
Vector images represent images using geometric shapes (such as lines, curves, circles, rectangles, etc.). These images use mathematical formulas (such as coordinates, angles, curvature, etc.) to describe the shapes, meaning they can be scaled up or down without losing image quality or detail. Common vector formats include SVG, AI, and EPS. Both the LDS PC and mobile versions support importing SVG vector images.
Normally, the Dithering effect is suitable for bitmap images with color or grayscale transitions.
A black-and-white image is also a type of bitmap, where each pixel only contains either black or white. If the imported image is a black-and-white image, it is recommended to select the Black and White effect to simplify the engraving process and improve efficiency.
However, if Dithering is selected, the software will perform more complex processing, and the engraving will take longer. (In the below screenshot, Fill represents Black and White effect and Picture represents Dithering effect. )
If the image only contains two or three colors with high contrast between adjacent colors, the Black and White effect is also a good choice. This is suitable for scenarios such as simple logos, cartoon images, or line drawings.
3. How to Use Dithering Effect in LDS
Importing an Image
Switching Image Effects
For imported images, you can adjust the image filter to achieve various image effects.
- Original: Restore the image to its original effect.
- Pencil: Converting the image into a sketch-like effect, resembling pencil drawings. Adjust the threshold to change the image display.
- B&W: Turning the image into high-contrast black and white. Adjust the threshold to change the image display. Clicking the Invert button will apply an inverse color effect to the image.
- Stamp: Creating a stamped, high-contrast effect with a mirrored appearance(Stamp mode will mirror the image horizontally and apply an inverse color effect). Adjust the threshold to change the image display.
- Emboss: Producing a 2D embossed visual effect, which makes the image appear raised or recessed. Adjust the intensity to enhance the 3D effect, making the raised or recessed details more pronounced.
- Sketch, Comic 1, Comic 2, and Halftone: These are additional artistic or comic-style effect filters provided by the software. You can switch between them and preview the effects to determine if they meet your needs.