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Questions tagged [contrast]

the difference in color and light between parts of an image

281 questions
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Converting Images to Black and White for Image Recognition in R

I'm trying to gain some experience with automatic text recognition and i'm using the package tesseract to perform ocr on some images (i.e. some screenshots I took). To improve the performance of my program's recognition of the prices in the image…
Francesco Dal Pont
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AA Level Accessibility - Colour Contrast boosted using text shadow

I have a site that I'm coding to WCAG 2.0 AA Level compliance and one of the buttons has a colour contrast that does not pass. Background - #D57405 Foreground - #FFF Is it possible to use text-shadow to boost the contrast – would that be seen as a…
Brent Dayman
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How can I adjust contrast in OpenCV in C?

I'm just trying to adjust contrast/ brightness in an image in gray scale to highlight whites in that image with Opencv in C. How can I do that? is there any function that makes this task in opencv? Original image: Modified image: Thanks in…
edsonlp1
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Faster contrast algorithm for a bitmap

I have a tool with trackbar slider controls used to adjust an image's brightness, contrast, gamma, etc. I am trying to get real-time updates to my image while the user drags the slider. The brightness and gamma algorithms are an acceptable speed…
Trevor Elliott
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contrast enhancement of an image using neighbourhoood

Hi I want to enhance the contrast of an image using the neighbourhood pixel values. Let the image be considered as u0. Then I want to enhance the image by using the formula Here, M1 is the minima and M2 is the maxima of u0 among the neighbourhood…
roni
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Default CSS filter values for brightness and contrast

Recently I've updated Chrome to v.26 and pictures which were displayed using HTML5 canvas were not visible anymore. As I found I had to change to brightness and contrast. How are the values for BC for CSS filters different depending on the browser…
Jacob
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Balancing contrast and brightness between stitched images

I'm working on an image stitching project, and I understand there's different approaches on dealing with contrast and brightness of an image. I could of course deal with this issue before I even stitched the image, but yet the result is not as…
JavaCake
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Automatically contrasting text color based on background image color

I'm looking for a way to change the color of text to either #000 or #fff depending on the main color of a background image within a div called "banner". The background images are chosen at random on each page so I need to be able to do this…
Justin
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partition of anova and comparisons (orthogonal single df) in r

I want to do single df orthogonal contrast in anova (fixed or mixed model). Here is just example: require(nlme) data (Alfalfa) Variety: a factor with levels Cossack, Ladak, and Ranger Date : a factor with levels None S1 S20 O7 Block: a…
SHRram
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Why does changing contrast type change row labels in R lm summary?

With the default contrasts in R (contr.treatment), the summary of a linear model object gives row names according to the level names. When I change the contrasts to contr.sum, the summary of the linear model object gives row names according to made…
Jdub
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Is there a standard sequence for gamma, brightness & contrast corrections?

In my application I'm doing gamma, brightness and contrast corrections defined by the user. Now I was wondering whether there is a standard order of doing this or not. It may sound trivial but I couldn't find anything regarding this. I guess it's…
user238801
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Convert from relative luminance to HSL

Given a certain color in HSL (let's say hsl(74,64%,59%)), I want to calculate what darker shade (with the same h and s values) gives me enough contrast to satisfy W3C color contrast requirements. There are formulas to convert HSL to RGB (for example…
Peter
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Mapping a list of numeric values to colors

I have a list of numeric values. I may normalize the values if needed. I need to transform this list to a list of colors (in HSL, RGB or any other color model — I can always do conversion later). For any given value the color must be the same every…
Alexander Gladysh
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Illumination normalization in OpenCV

I am working on a face recognition project. I have pictures with different lighting so I need to do illumination normalization. I read a paper which which claims to do illumination normalization. The paper describe the following function and values.…
Shah
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Contrasts for lm using contrast package

I'm using contrast package to construct contrasts for lm in R. With the following code I'm making contrast between Trt1 and Trt3. Y <- c(10, 12, 14, 16, 9, 8) Trt <- gl(n=3, k=2, length=3*2) Data1 <- data.frame(Y, Trt) Data1.lm <- lm(Y~Trt, data =…
MYaseen208
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