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Text of the page (random words):
ok like another more power curve for shadow mid and highlights with four numbers we can tweak the bottom top and somewhere in the middle more k clustering a process module for k means fuzzy k means and k harmonic with transparency more sparse hald cluts and completing them more editing with hald cluts a brief introduction more set mean and stddev setting lightness and contrast and colour without clipping using power and sigmoidal contrast more windowed mean and standard deviation some methods fast and slow coarse and smooth more crop to detail a method for automatic cropping more integral images for windowed mean and sd more scale rotate and translate in 3d a simple but effective method more watermarks adding and removing them more coordinates of a colour what are the coordinates of pixels of a given colour more lines points and curves wobbly raster lines can be expressed as ordered sets of coordinates and simplified to vectors more seamless photomontage poisson image editing and related techniques more pin or push we can push pixels to new locations while pinning others in place more slopes a simple scheme for creating storing and processing slopes more lithographic effects im can make images in the style of simple lithographs halftone silk screen etching lino printing engraving and similar processes more searching an image aggressively searching quickly for the location of a small sub image inside a much larger image more by fft what rotation using fft we find relative rotation of images invariant to scale translation or other factors more sound and vision sound is an image with one dimension more perceptual hash thresholds we experiment with rms thresholds that classify image pairs as same or different more perceptual hash tests experiments with im s perceptual hash with suggestions for improvement more flat colour cartoons we replace each area of similar but varying colour with a single representative colour more partition boundary masks we partion an image into areas of flat or slowly changing colour more cartoon and texture an image can be deconstructed into a cartoon and texture more find four corners three simple methods more mending broken lines three methods are shown more pruning skeleton stubs skeleton images often contain stubs short segments at the ends or along their length this method removes them more random lines these are sometimes useful more curving in 3d we distort the image plane like curving a piece of paper more subimage rectangles an image that has been built from smaller rectangular images can be segmented back into those images more setting the mean we can tweak an image to match the brightness and colour of another more mosaicing we can make bayer mosaic images from ordinary colour images more alignment by gaussian pyramid brute force alignment of corresponding levels of gaussian pyramids finds a good translation only alignment fairly quickly more laplacian pyramids with transparency images with transparency need special processing when making laplacian pyramids more detail by pyramids laplacian pyramids give us frequencies at which data occur more blending pyramids images can be blended by making laplacian pyramids blending these to make a third and collapsing it more squishing images when images have transparent areas we can append such that opaque areas abut each other more inverse composites if a known image was composited with an unknown image making a known result how can we find the unknown more quilting we can build an image by quilting together ragged cut rectangles from a texture image more assembling with dark paths images can be assembled in grid patterns with minimum error boundary cuts more awkward boundaries with dark paths an image can be cut by a single dark path to make a piece that will sit with small boundary error on another image more tiling with dark paths an image can be cut by dark paths to make a ragged edge piece that will tile with itself in both shape and colour more rectangle boundaries with dark paths an image can be cut by up to four dark paths to make a piece that will sit with small boundary error on another image more dark paths dark paths solve some minimization problems and create sequences for animation and other purposes more haar wavelet pyramids a blast from the past alfred haar invented these in 1909 more filling holes in priority order filling pixels in priority order improves quality more filling holes a process module estimates colours for transparent pixels by cloning colours from elsewhere in the image more gain and bias we can tweak an image to match the brightness and colour and contrast of another more alignment by brute force the alignment of two images can be tested at every possible offset more fractal noise animations fractal or perlin noise can be animated more fractal noise fractal or perlin noise is coherent and self similar at different scales more multi scale pyramids an image can be represented by a multi scale pyramid more animation with srt distort srt provides simple but high quality animation more color cycle tests this page is automatically created by the script colcycltst bat see colour cycling tests more colour cycling cycling colours with different methods gives results that satisfy certain criteria more noise noise adds noise here are some illustrations more nearest coastal point from a given coordinate we can find the nearest point in an arbitrary area more polar distortions distorting polar coordinates r θ is conveniently done by first transforming to cartesian y x distorting y or x then transforming back more coffee mug how can we superimpose an image on to a coffee mug if the mug can be modelled in pov ray there are two obvious methods more outputs speed and size for simple image processing writing the output can take a significant proportion of the overall time more straightening horizons when an image has a wobbly line that is roughly horizontal we can distort the image such that the line becomes straight and horizontal more follow line we can distort an image perhaps representing fabric so the central line follows an arbitrary path and do the inverse more gradient contours a grayscale gradient image can be made more readable by showing contour lines or lines perpendicular to contours more fifty percent the mid point of zero and an odd number is not an integer so 50 gray with integer im cannot be exactly 50 more triangulation two new features could be added to imagemagick distort triangulate and sparse colour triangulate more histogram peaks when histogram data is stored as images we can manipulate it with image processing techniques more dcraw gamma and eqlimit what are the best dcraw gamma and auto brighten settings for various purposes more adaptive contrast limited equalisation equalising an image is often useful but can uglify photographs when the contrast introduced by equalisation is limited results are more pleasing the process can be adapted across the image more adaptive auto level and gamma we can auto level and auto gamma as appropriate for different parts of an image blending between these parts more blending tiles an image may have a number of variations based on characteristics of the image divided into cells or a regular crop then we want to blend these variations together more pango imagemagick can rasterise a simplified version of html more canny edge detection canny and other types of edges can segment images more levels we can do a linear transformation of levels by using either level or level with a suitable change of parameters for some situations it isn t obvious which of these we should use more orientation jpegs from cameras are often wider than they are high with metadata that specifies the true orientation but software often ignores this metadata so viewers don t display or process as we would hope this script normalises orientations more knots we can draw pretty pictures of knots more old documents old documents often have little contrast between ink and paper the paper may not be a constant colour or tone we might want to prettify the document making it more visually attractive or we might want to increase the legibility we might want to make the paper white and the ink black more camera blurs digital blurring is usually gaussian or something close cameras defocus differently more shape to shape we can distort a shape to match another shape more resampling with halo minimization resizing an image can create halo artifacts these can be reduced by blending two results more growcut segmentation images can be segmented broken into pieces clustered according to the similarity of adjacent pixels the growcut method grows clusters from pre defined seeds according to the strength or weighting of cluster membership more process modules we can customise imagemagick to add new functionality for example with process using magickcore like plug ins i show some examples more compiling the magickwand demonstration programs im demo programs can be compiled with cygwin tools more compiling im with cygwin im can be compiled with cygwin tools more im with cygwin im can run under cygwin which provides a unix like environment under windows more statistics here is a process i use for detecting outliers in a series such as the transformations from points in one image to points in another by rejecting outliers we improve the overall transformation more islands suppose we have an arbitrary black shape and an arbitrary black border the shape is an island it is surrounded by white the black border extends to the image edges it is a mainland more alignment by matching points when the camera has twisted around the z axis between photographs registering the images is difficult no areas in one image match areas in the other we want to find alignment when the image has scaled rotated translated and perspectived more simple alignment by matching areas when we have a list of interesting points in one image we can locate matching areas in another image making the assumption that any rotation and scaling is small the assumption is true if the camera is hand held but not moved much such as frames from a video or stills intended for a panorama more colour temperature we can shift the colour temperature of an image perhaps to compensate for light sources by manipulating the colour channels more zipped bat files for convenience scripts and c functions are available in a single zip file more demosaicing in most digital cameras each sensor element records either red or green or blue these are arranged in a mosaic a critical part of processing raw camera images is demosaicing which amounts to guessing suitable values for the other two channels at each pixel more what translation given two images of the same size where one image could be a translation of another image with a known scale and rotation what are the best offsets more what rotation and scale given one image that could be a rotation and scale of another image what is the best rotation angle and scale factor more what scale given one image that could be another image rescaled what is the best scale factor more what rotation given one image that could be a rotation of another image what is the best rotation angle more searching an image searching for the location of one image inside another is very easy doing it quickly is harder more details details detail draws the eye into a photograph or distracts the gaze it is also useful for aligning registering photos or video frames more adding zing to photographs sometimes a photograph needs more zing more pop aesthetic decisions are difficult to quantify and harder to automate but here are some tools aimed at large images derived from raw camera files more cylinders we can displace a rectangular image so it appears to be on the face of a cylinder or go in the opposite direction more svg text imagemagick is a wonderful non interactive tool for processing raster images with inkscape it can do fancy things with text in svg files more de barrel distortion i love gopro cameras including the fisheye effect heavy barrel distortion if we want we can make the image rectilinear removing this distortion more greyscale gamma rgb srgb imagemagick has two colorspaces of particular importance srgb non linear and rgb linear some people argue that operations should be performed in rgb space not srgb this is my take on the subject more panel of nine interactive image editors allow us to tweak a slider to adjust an effect imagemagick is non interactive but here are simple scripts to quickly see the effect of adjustments without needing complex javascript or whatever more gradients cookbook this page is mostly about two dimensional greyscale gradients ranging from black to white that have different values for both x and y dimensons they are useful as masks for processing photographs for video transitions and a variety of graphics effects more displacement maps this is a method for moving pixels for every destination pixel we specify where it should be copied from more making an image grayscale monochrome imagemagick has an infinite number of ways of converting a colour image to monochrome however it provides a smaller number of simple methods more clut cookbook many methods for creating nx1 colour look up tables more colorspace cookbook imagemagick can change colorspaces we can examine the effect of a round trip from srgb to another colorspace and back both pictorially and numerically more composite compositions we can manipulate and combine compositions for new operations such as equals and greater than more utf 8 characters imagemagick can rasterise utf 8 characters outside the ascii range 0 127 more hdri imagemagick can handle high dynamic range images it does this by storing and processing pixels as floating point numbers instead of integers more snippets here are some short windows bat command files mostly using imagemagick that i find useful for processing images i use some as they stand or copy and paste the commands into a more complex script some of these are used every day and some are failed experiments i have thrown them all together you have been warned more colour wheels we can draw some pretty colour wheels more inner trim sometimes we want to entirely remove an uneven border in other words we want to find a rectangle that contains a constant colour more gimp and im gimp is a interactive image editor useful for experimenting with effects and verifying results it is limited to 8 bits per channel which is a major limitation for serious processing more selective blur we sometimes want to vary the amount of blur across an image perhaps by using a mask maximum blur where the mask is white and no blur where the mask is black more windows for command compose operators de mystified or perhaps mystified even further the pages are all works in progress and i often add material each page has a page created date at the bottom this is autom...