DIP CH5.pdf

Digital Image processing Ch5 IMAGE FILTERING Lecturer Mohammed Al-kahlout 1 Using filters You can use filters to clean up or retouch your photos, apply special art effects that give your image the appearance of a sketch or impressionistic painting, or crea...

Digital Image processing Ch5 IMAGE FILTERING Lecturer Mohammed Al-kahlout 1 Using filters You can use filters to clean up or retouch your photos, apply special art effects that give your image the appearance of a sketch or impressionistic painting, or create unique transformations using distortions and lighting effects. 2 Filtering definitions Image filtering changes the range (i.e. the pixel values) of an image, so the colors of the image are altered without changing the pixel positions, while image warping changes the domain (i.e. the pixel positions) of an image, where points are mapped to other points without changing the colors. Image filtering is changing the appearance of an image by altering the colors of the pixels. 3 How filters work In digital image processing, thresholding is the simplest method of segmenting images. From a grayscale image, thresholding can be used to create binary images. 4 How filters work Basic thresholding methods replace each pixel in an image with a black pixel if the image intensity 'I' is less than some fixed constant 'T', or a white pixel if the image intensity is greater than that constant. 5 How filters work Simple thresholding… For every pixel, the same threshold value is applied. If the pixel value is smaller than the threshold, it is set to 0, otherwise it is set to a maximum value. 6 How filters work Threshold Value: value that sets a limit or boundary, above or below which a different state or condition is observed. 7  Filters guidelines Filters are applied to the active, visible layer or a selection. For 8-bits per-channel images, most filters can be applied cumulatively through the Filter Gallery. All filters can be applied individually. Filters cannot be applied to Bitmap-mode or indexed-color images. Some filters work only on RGB images. All filters can be applied to 8-bit images. 8 Filters guidelines The following filters can be applied to 16-bit images: Liquify, Vanishing Point, Average Blur, Blur, Blur More, Box Blur, Gaussian Blur, Lens Blur, Motion Blur, Radial Blur, Surface Blur, Shape Blur, Lens Correction, Add Noise, Despeckle, Dust & Scratches, Median, Reduce Noise, Fibers, Clouds, Difference Clouds, Lens Flare, Sharpen, Sharpen Edges, Sharpen More, Smart Sharpen, Unsharp Mask, Emboss, Find Edges, Solarize, De- Interlace, NTSC Colors, Custom, High Pass, Maximum, Minimum, and Offset. The following filters can be applied to 32-bit images: Average Blur, Box Blur, Gaussian Blur, Motion Blur, Radial Blur, Shape Blur, Surface Blur, Add Noise, Clouds, Lens Flare, Smart Sharpen, Unsharp Mask, De-Interlace, NTSC Colors, Emboss, High Pass, Maximum, Minimum, and Offset. 9 Blur filters The Blur filters soften a selection or an entire image, and are useful for retouching. They smooth transitions by averaging the pixels next to the hard edges of defined lines and shaded areas in an image. 10 Blur filters Average Finds the average color of an image or selection, and then fills the image or selection with the color to create a smooth look. Blur and Blur More Eliminate noise where significant color transitions occur in an image. Blur filters smooth transitions by averaging the pixels next to the hard edges of defined lines and shaded areas. Box Blur Blurs an image based on the average color value of neighboring pixels. This filter is useful for creating special effects. You can adjust the size of the area used to calculate the average value for a given pixel; a larger radius results in greater blurring. 11 Blur filters Lens Blur Adds blur to an image to give the effect of a narrower depth of field so that some objects in the image stay in focus and others areas are blurred. Motion Blur Blurs in the specified direction (from –360º to +360º) and at a specified intensity (from 1 to 999). Radial Blur Simulates the blur of a zooming or rotating camera to produce a soft blur. Choose Spin to blur along concentric circular lines, and then specify a degree of rotation. 12 Blur filters Shape Blur Uses the specified kernel to create the blur. Smart Blur Blurs an image with precision. You can specify a radius, a threshold, and a blur quality. Surface Blur Blurs an image while preserving edges. This filter is useful for creating special effects and for removing noise or graininess 13 Distort filters The Distort filters geometrically distort an image, creating 3D or other reshaping effects. Diffuse Glow uses the active background color to highlight lighter areas of the image, fading as it spreads out. Displace Uses an image, called a displacement map, to determine how to distort a selection 14 Distort filters Glass Makes an image appear as if it were being viewed through different types of glass. Twirl Rotates a selection more sharply in the center than at the edges. Wave shifts the pixels in a defined wave pattern. ZigZag Distorts a selection radially, depending on the radius of the pixels in your selection. 15 Noise Filters These tools are essential for improving image clarity and achieving professional results. UNDERSTANDING NOISE TYPES: Before applying filters, it's crucial to recognize the different types of noise: luminance noise and color noise. Each type affects image quality differently, requiring specific techniques for removal. 16 Noise Filters Reduce Noise filter is a powerful tool for smoothing out unwanted noise. Adjust settings like Strength, Preserve Details, and Reduce Color Noise to achieve a balance between clarity and detail 17 Noise Filters Median Filter is effective for reducing noise while preserving edges. By replacing each pixel's value with the median value of surrounding pixels, it can enhance image clarity. This technique is particularly useful for portrait and landscape photography. 18 Render Filters render filters are designed to create unique effects by simulating natural phenomena. These filters can transform ordinary images into extraordinary visuals. Key filters include Lens Flare, Clouds, and Lighting Effects, each providing distinct enhancements to your artwork. 19  Render Filters Lens Flare filter adds a realistic light source to your images. To apply it effectively, position the flare where light naturally occurs. Adjust the brightness and color to achieve a harmonious look that complements your design 20 Render Filters Clouds filter generates soft cloud textures, perfect for backgrounds. By adjusting the opacity and blending modes, you can create depth and atmosphere in your designs. 21 Render Filters Lighting Effects filter allows you to simulate various light sources in your artwork. By manipulating the angle, intensity, and color of the light, you can create a three-dimensional feel. 22 Sharpen Filters These tools enhance image clarity and detail, making your photos more impactful. 23 Sharpen Filters Unsharp Mask filter works by increasing contrast along the edges of an image. Adjusting the Amount, Radius, and Threshold settings allows for precise control over the sharpening effect 24 Sharpen Filters Smart Sharpen filter provides advanced control over sharpening. It allows you to adjust the shadow and highlight areas separately, which can help preserve details in both light and dark regions. 25 Thank you 26