How I can view this .tif file?

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BN 2020-4-13

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评论： Diego Mauricio Beramendi Ortega 2022-6-28

I have a tif file which represents the altitude for a country, I can simply open it in Esri's ArcGIS (Arc Map), Here is the result from ArcMap:

You can see the High and Low elevations are shown by a color range. I used this code below to open this tif file in Matlab:

x = imread('DEM_30s.tif', 'tif');
imshow(x)

But I see a figure like this:

So, If anyone could tell me how I can read my tif file in Matlab with a color bar that specifies high and low elevations (like Arcmap picture above), I would be so grateful.

Note: Since the size of the file is 7 MB, I split it into the 2 part then attach here; I also upload the .tif in my google drive in this link and compressed version of it (.zip) (just one part) here in my google drive.

Thank you

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KALYAN ACHARJYA 2020-4-13

编辑：KALYAN ACHARJYA 2020-4-13

Have you tried this?

https://www.mathworks.com/help/map/ref/readgeoraster.html

BN 2020-4-13

Dear KALYAN ACHARJYA

Yes, Please see my first comment above (https://www.mathworks.com/matlabcentral/answers/517443-how-i-can-view-this-tif-file#comment_826670)

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采纳的回答

Ameer Hamza 2020-4-13

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https://ww2.mathworks.cn/matlabcentral/answers/517443-how-i-can-view-this-tif-file#answer_425748

编辑：Ameer Hamza 2020-4-13

在 MATLAB Online 中打开

First, the problem is somewhat related to the encoding of your tiff file. The data values are encoded as single-precision numbers, and the background points are encoded as 0xff7fffff in hexadecimal (equal to -3.40282346639e+38, minimum possible number in IEEE754 single-precision floating-point format).

Second, the tiff file only has 1 channel, and have no color information, so you need to create your colormap.

Both problems can be solved by converting the loaded matrix from single to uint16. Note that we are converting the values, not typecasting. Converting to uint16 will convert the background pixels from -3.40282346639e+38 to 0. The elevation values lie in the range [0 - 10000], uint16 is sufficient to hold these values. The integer values will make it an indexed image that can take value from a colormap. Try the following code

[A,R] = readgeoraster('DEM_30s.tif', 'OutputType', 'double');
low_single = typecast(uint8([255 255 127 255]), 'single');
mask = low_single==A;
A = A - min(A(~mask), [], 'all');
% creating colormap changing from white to brown as shown in image in the question
brown_color = [0.8 0.2 0.1];
light_brown = [0.95 0.9 0.8];
t = linspace(0, 1, max(A,[],'all'))';
cmap = t.*brown_color + (1-t).*white;
gs = geoshow(A, cmap, R);
gs.CData(repmat(mask,1,1,3)) = 255;

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BN 2020-4-13

编辑：BN 2020-4-13

在 MATLAB Online 中打开

Y.mat
X.mat

Dear Ameer Hamza,

First of all, I want to thank you for reading my question and answering. It's solved my problem, thank you. Actually I have 2 quick questions:

1. So the elevation in the generated figure is the same as the arc map results? (I ask this because I thought there were some elevations under 0 (I mean under the sea level) in the country but you said elevation values lie in the range [0 - 10000]. However, the figure really seems like arc map image.

2. I extracted X and Y of the country from its shapefile and plot a border around it using this code,

hold on
plot (X,Y,'-','color','k')

The result is: ( I changed white to very very light brown):

Do you think it is possible to change all colors outside the country to white? In this way, I can set any color instead of white for low elevations, for example, brown and yellow (without changing the background of all figure to yellow). Also is it possible to have a correct color bar?

Really Appreciate and Thank you a lot.

Best Regards