I am facing an issue in which I have to dynamically set the font color regarding the background image brightness.
For instance, if the background image is dark, I would put font color on 'white'.
Is there any tool that can give my the brightness of the image using React-Native?
This seems to be a similar question as mentioned in How to access image pixel data in react-native
Step 1
The marked answer shows a solution in wich create a native (android) function wich returns a object that contains among other things an array filled with the color of every pixel (width, height, hasAlpha and pixels).
Step 2
I am no graphic designer so I am not a 100% sure if this is correct but it sounds ok. As mentioned in the question Image Dark/Light Detection Client Sided Script
JavaScript provides a function that converts each color to gray scale and then returns an average pixel. I don't actually know if react-native provides this function - try it and then I will change the answer to this step.
Step 2.1 - Converting to gray scale
I my understanding it's just that easy:
* Indigo Color Example as you can see in the color detail you have 3 different parts - R (81) G (43) B (219)
* Add these three for each pixel and divide them with 3
* 81+43+219 = 343 / 3 = 114,3 -> 114 = grayscale
Step 2.2 - Adding all grayscales together and divide through sum
All your pixel should be able to transfaired into grayscale. There you can go and add them together and divide it through the amount of pixels you got
Step 3
There is my most questionable point where you maybe have to try it yourself. I would say if 0 is the minimum (dark) and 255 is the maximum (white) the middle 127 is where you decide if the color is dark or white
Examples for dark or light colors
127 is where we decide to go dark or light
Misty Rose graycolor = 236 = light
Indigo Color Example graycolor = 114 = dark
#46bfb0 graycolor = 145 = light
Misty Rose 4 graycolor = 129 = light
#72632f graycolor = 87 = dark
This short experiment by me showed me that 127 as line is maybe not perfect if you look at #46bfb0 it could be dark instead of light - so test it out and please commend your solutions with this project.
Related
I have been trying to use opencv's template matching function to match templates within images. However, when the images are dark brown and dark green, the template matching does not work so well. I am pretty sure it is the grey scale conversion that is responsible for this because in greyscale it looks very similar.
However from what I see, cv2.matchtemplate() only takes in grey scale images. How can I do coloured template matching? Should I seperate the RGB image into 3 images: one red, one green, one blue and treat each one as gray scale images and apply matchtemplate then sum the similarity rating for each pixel position? Is that the way to do it? Or is there a different function or a parameter value I can use to make matchtemplate work for coloured images?
You may try this code:
import numpy as np
import cv2
threshold = 0.8
##Read Main and Needle Image
imageMainRGB = cv2.imread(main/Image/Path/main.png)
imageNeedleRGB = cv2.imread(needle/Image/Path/needle.png)
##Split Both into each R, G, B Channel
imageMainR, imageMainG, imageMainB = cv2.split(imageMainRGB)
imageNeedleR, imageNeedleG, imageNeedleB = cv2.split(imageNeedleRGB)
##Matching each channel
resultB = cv2.matchTemplate(imageMainR, imageNeedleR, cv2.TM_SQDIFF)
resultG = cv2.matchTemplate(imageMainG, imageNeedleG, cv2.TM_SQDIFF)
resultR = cv2.matchTemplate(imageMainB, imageNeedleB, cv2.TM_SQDIFF)
##Add together to get the total score
result = resultB + resultG + resultR
loc = np.where(result >= 3 * threshold)
print("loc: ", loc)
The Image I tested with are:
main.png
needle.png
result.png
Remark: This code may not function in some photos, where a user may need to modify it further to enhance it.
Note: This image was getting from pexels.com which is free copyright. If you have any issues with the image copyright and want to take down this image, welcome to contact me. Thanks.
I am trying to get ImageMagick to do something for me and I am running into a few problems. First, I am not understanding units of measure and such passed into ImageMagick and so my script is not producing what I need. Second, the way I am doing it is extremely inefficient. Running this script takes a very long time (the one you see below is slightly trimmed down from what I am running).
So to what I am doing... I have a number of svg files with icons in them. I am looking to generate a page for each of these files. The page generated will contain the icon tiled over the entire page with a margin on the side. I am looking for 1/2 inch tiles with 1/2 margins around the page which needs to be a US Letter (8 1/2 x 11 inch).
After reading a lot of the documentation this is what I came up with.
colors=(red blue purple yellow green black)
mkdir -p generated/icons/
for color in ${colors[#]}; do
images=`printf "source/icons/${color}.svg%.0s " {1..300}`
montage $images -tile 15x20 -page Letter+1+1 -units PixelsPerInch -density 2550x3300 \
generated/icons/${color}.pdf
done
So for each of my files I run montage. I use printf to repeat the image file name 300 times. I then tile this 15x20 times. 15x20 comes from 8.5 minus 1 inch margins = 7.5*2 = 15 and likewise (11-1)*2 = 20. 300 images come from 15*20. I then say I want this on a letter page offset 1x1. (This was my attempt at a margin) I say I am speaking in pixel per inch (but none of the units seem to match up). I set the dpi to 300 by the density command where 8.5*300 = 2550 and 11*300 = 3300.
I've been toying with other settings (geometry etc.) but none of these are working. And the units don't seem to make sense either... Right now my resultant pdf is a square etc...
How do I make tiled pages as such? Also is there a way for me to do this more efficiently? What I have thus far is very slow.
EDIT:
Some more information:
i:montage --version
Version: ImageMagick 6.8.8-10 Q16 x86_64 2015-03-10 http://www.imagemagick.org
tile image:
my current output:
Notice margins not right, is square not a letter page, also tiles as skewed
Given the PNG image you provided, and I presume you want a 1 inch border of white all around inside an 8.5x11 inch printed image. Thus the tiled width would be 7.5 inches and tiled height would be 10 inches.
1 in = 300 dpi so border thickness = 300 px = 2 tiles thick
11-1 = 10 inches tall for tiled region height = 10*300 = 3000 px
8.5-1 = 7.5 inches wide for tiled region width = 7.5*300 = 2250 px
1 tile = 0.5 inches at 300 dpi = 0.5*300 = 150 px
convert lUDbK.png -resize "150x150!" -write mpr:tile +delete -size 2250x3000 tile:mpr:tile -bordercolor white -border 300 -units pixelsperinch -density 300 tiled_page.png
Time to process was 1.75 sec on my Mac Mini.
This produces an image which is rather large. You will have to extract the image to see the border, since this page background is white.
(Note that PNG only supports pixelspercentimeter, but IM converts my specification of pixelperinch accordingly. So if you look at the meta data, it will probably show you some other density in units of pixelspercentimeter. But they will correspond to the desired 300 dpi.)
Ok, I have a ScrolledWindow with inside a Viewport and a Fixed inside of that. I'm using the Builder so I'm not gonna post ALL the code if is not necessary.
I'm using a function that multiplies the given coordinates per 50, so i have a grid with 50 x 50 pixel's squares (the number of squares can variate in the config).
The real question is very simple, how I can put a background of a grid of 50 per 50 pixels? And that should be """infinite""". Preferly the lines should be of 1 px.
Note: I'm not using a grid because I need only to put Images or Icons
I used that. Mainport is the fixed element, and wres and hres are the number of squares
for i in range(self.wres):
image = gtk.Image.new_from_file("resources/Back.png")
self.mainport.put(image, i*50, 0)
for z in range(self.hres):
image2 = gtk.Image.new_from_file("resources/Back.png")
self.mainport.put(image2, i*50, z*50)
I have searched extensively online and I have the PDF specification in which I have looked, yet I still can't figure out how to draw a simple black line on a PDF page from the content object's instructions (stream).
Let's say I just want to draw a 1-pixel thickness (assuming 72 dpi) black line at x 400, y 100-300.
This should in theory be a very simple operation, but the PDF spec goes on and on about all kinds of fancy things and appears to forget to explain how I would go about performing this simple operation.
Please can someone point me in the right direction?
In the PDF specification, have a look at chapter 8 (Graphics) and in there section 8.5, Path Construction and Painting.
To draw a simple straight path, you need a "move to" operation followed by a "line to" operation:
400 100 m
400 300 l
You can then stroke the path using the S operator so your code becomes
400 100 m
400 300 l
S
By default the color is black so you've already gotten a black line :-) But if you want to make sure you have to set some parameters in the graphics state.
0 G
1 w
400 100 m
400 300 l
S
The first line now sets the color space to "gray" and puts the shade of grey to 0 (black). The following line sets the line width of your stroked line to 1 user unit (what this comes out as is dependent on your current transformation matrix.
You can apply a neat trick if you really want 1 pixel (please don't for production files though!) and that is to set the width to zero:
0 w
This gives you "the thinnest line that can be rendered at device resolution: 1 device pixel wide".
I have a physical map (real world), for example, a little town map.
A "path" line is painted over the map, think about it like "you are here. here's how to reach the train station" :)
Now, let's suppose I can get an image of that scenario (likewise, coming from a photo).
An image that looks like:
My goal is not easy way out!
I want to GET the path OUT of the image, i.e., separate the two layers.
Is there a way to extract those red marks from the image?
Maybe using CoreGraphics? Maybe an external library?
It's not an objective C specific question, but I am working on Apple iOS.
I already worked with something similar, the face-recognition.
Now the answer I expect is: "What do you mean by PATH?"
Well, I really don't know, maybe a line (see above image) of a completely different color from the 'major' colors in the background.
Let's talk about it.
If you can use OpenCV then it becomes simpler. Here's a general method:
Separate the image into Hue, Saturation and Variation (HSV colorspace)
Here's the OpenCV code:
// Compute HSV image and separate into colors
IplImage* hsv = cvCreateImage( cvGetSize(img), IPL_DEPTH_8U, 3 );
cvCvtColor( img, hsv, CV_BGR2HSV );
IplImage* h_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
IplImage* s_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
IplImage* v_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
cvCvtPixToPlane( hsv, h_plane, s_plane, v_plane, 0 );
Deal with the Hue (h_plane) image only as it gives just the hue without any change in value for a lighter or darker shade of the same color
Check which pixels have Red hue (i think red is 0 degree for HSV, but please check the OpenCV values)
Copy these pixels into a separate image
I's strongly suggest using the OpenCV library if possible, which is basically made for such tasks.
You could filter the color, define a threshold for what the color red is, then filter everything else to alpha, and you have left over what your "path" is?