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Blurs the active image or selection. This filter replaces each pixel with the average of its 3x3 neighborhood.Sharpen
Increases contrast and accentuates detail in the image or selection, but may also accentuate noise. This filter uses the following weighting factors to replace each pixel with a weighted average of the 3x3 neighborhood.-1 -1 -1 -1 12 -1 -1 -1 -1Find Edges
Uses a Sobel edge detector to highlight sharp changes in intensity in the active image or selection. Two 3x3 convolution kernels (show below) are used to generate vertical and horizontal derivatives. The final image is produced by combining the two derivatives using the square root of the sum of the squares.1 2 1 1 0 -1 0 0 0 2 0 -2 -1 -2 -1 1 0 -1Enhance Contrast
Does a linear histogram stretch to enhance the contrast of the image. If there is a selection, the entire image in enhanced based on the histogram of the selection. Repeated use of this command will continuously increase image contrast.Noise>
Use the commands in this submenu to add noise to images or remove it.
Add Noise
Adds random noise to the image or selection. The noise is Gaussian (normally) distributed with a mean of zero and standard deviation of 25.Add More Noise
Adds Gaussian noise with a mean of zero and standard deviation of 75.Salt and Pepper
Adds salt and pepper noise to the image or selection by randomly replacing 2.5% of the pixels with black pixels and 2.5% with white pixels. Note: this command only works with 8-bit images.Despeckle
This is a median filter. It replaces each pixel with the median value in its 3 x 3 neighborhood. This is a time consuming operation because, for each pixel in the selection, the nine pixels in the 3x3 neighborhood must be sorted and the center pixel replaced with the median value (the fifth). Median filters a good at removing salt and pepper noise.Shadows>
Commands in this submenu produce a shadow effect, with light appearing to come from a direction corresponding to the command name. The commands use Convolve3x3, ImageJ's 3x3 convolution function. Two of the convolution kernels are shown in the illustration. Shadows Demo uses all eight kernels to demonstrate the speed of Convolve3x3.
Morphology>
This submenu contains morphological filters that manipulate the shape of objects. With the exception of Outline and Skeletonize, they work with binary, grayscale and color images. With binary images, they assume objects are black and the background is white.
Threshold
Converts grayscale images to black and white and color images to the eight primary colors. The threshold level is determined by analysing the histogram of the current selection, or of the entire image if there is no selection. Uses a technique described originally by Ridler & Calvard in "Picture Thresholding Using an Iterative Selection Method", IEEE transactions on Systems, Man and Cybernetics, August, 1978.Erode
Replaces each pixel with the minimum (lightest) value in the 3x3 neighborhood. With binary images, removes pixels from the edges of black objects. With grayscale and color images, reduces the size of objects that are darker than background.Dilate
Replaces each pixel with the maximum (darkest) value in the 3x3 neighborhood. With binary images, adds pixels to the edges of black objects. With grayscale and color images, increases the size of objects that are darker than background.Open
Performs an erosion operation, followed by dilation. With binary images, this smoothes objects and removes isolated pixels.Close
Performs a dilation operation, followed by erosion. With binary images, this smoothes objects and fills in small holes.Set Iterations...
Allows you to specify the number of times erosion, dilation, opening, and closing are performed. The default is one.Outline
Generates a one pixel wide outline of black objects in a binary image.Skeletonize
Repeatably removes pixels from the edges of objects in a binary image until they are reduced to single pixel wide skeletons. Objects are assummed to be black and backgound white.
Math>
The commands in this submenu add (subtract, multiply, etc.) a constant to each pixel in the active image or selection. When the result value overflows/underflows the legal range of the image's data type, the value is reset to the maximum/minimum value. With stacks, selections are ignored and the specified operation is performed on all slices in the stack.Add...
Adds a constant to the image. With 8-bit images, results greater than 255 are set to 255. With 16-bit signed images, results greater than 32,767 are set to 32,767.Subtract...
Subtracts a constant from the image. With 8-bit images, results less than 0 are set to 0. With 16-bit signed images, results less than -32,768 are set to -32,768.Multiply...
Multiplies the image by the specified real constant. With 8-bit images, results greater than 255 are set to 255. With 16-bit signed images, results greater than 32,767 are set to 32,767.Divide...
Divides the image by the specified real constant. Attempts to divide by zero will be ignored.AND...
Does a bitwise AND of the image and the specified binary constant.OR...
Does a bitwise OR of the image and the specified binary constant.XOR...
Does a bitwise XOR of the image and the specified binary constant.Gamma...
Applies the function f(p) = (p/255)^gamma*255 to each pixel (p) in the image or selection, where 0.1 <= gamma <= 5.0. For RGB images, this function is applied to all three color channels. For 16-bit images, the image min and max are used for scaling instead of 255.Log...
Applies the function f(p) = log(p) * 255/log(255) to each pixel (p) in the image or selection. For RGB images, this function is applied to all three color channels. For 16-bit images, the image min and max are used for scaling instead of 255.Reciprocal
Generates the reciprocal of the active image or selection. Only works with 32-bit real images.Image Calculator...
Performs arithmetic and logical operations between two images selected from pop-up menus. The destination or both the source and destination can be stacks. If both are stacks, they must have the same number of slices. The source and destination images must be the same data type but do not have to be the same size.You can select one of 12 operators from the Operation: pop-up menu. The result of the operation replaces some or all of the destination image.
Add dst = src+dst Subtract dst = dst-src Multiply dst = src*dst Divide dst = dst/src AND dst = src AND dst OR dst = src OR dst XOR dst = src XOR dst Min dst = dst = min(src,dst) Max dst = dst = max(src,dst) Average dst = (src+dst)/2 Difference dst = (dst-src)/2+128 Copy dst = src In these examples, the source and destination have inverted LUTs so zero pixels are white. Operations on images with non-inverted LUTs, and RGB images, will not produce the same results.
Subtract Background...
Removes smooth continuous backgrounds from gels and other images. Uses a rolling ball algorithm inspired by Stanley Sternberg's article, "Biomedical Image Processing", IEEE Computer, January 1983. Based on NIH Image Pascal code written by Michael Castle and Janice Keller of the University of Michigan Mental Health Research Institute. The Rolling Ball Radius should be at least as large as the radius of the largest object in the image that is not part of the background.Repeat Command
Reruns the previous command. The Undo and Open commands are skipped. For a shortcut, type shift-R.