OpenCV imwrite params read access violation

Question

A very simple question...why am I getting a read access violation error with this code?

cv::Mat laserSpeckle = Mat::zeros(100,100,CV_8UC1);
imwrite( "C://testimage.jpg", laserSpeckle );

When i attach a debugger and look into it further, it throws the exception at this snippet in grfmt.cpp.

if( params[i] == CV_IMWRITE_JPEG_QUALITY )
        {
            quality = params[i+1];
            quality = MIN(MAX(quality, 0), 100);
        }

It occurs with .png and .tiff too. Im an OpenCV newbie, my apologies if this is something really simple. I am using Qt for what its worth.

Why does the destination path has two forward slashes (//)? Windows addresses paths with back slash (), but since it is the "escape" character on programming, we have to use two of them together "\\". — gibertoni
– gibertoni, Commented Mar 26, 2015 at 19:41
my mistake...changing them to two backslashes made no difference though. — user1003131
– user1003131, Commented Mar 26, 2015 at 19:46
Windows can use forward slashes for most file operations unless you need the extended path lengths using the ` "\\?\"` prefix. — drescherjm
– drescherjm, Commented Mar 26, 2015 at 19:50
are you compiling in debug or release mode? are you linking against debug or release mode of openCV libraries? — Micka
– Micka, Commented Mar 27, 2015 at 8:59

nils · Accepted Answer · 2015-03-29 11:13:36Z

2

Do you build OpenCV yourself? If yes, make sure that the option WITH_JPEG is enabled when you configure your build files:

cmake ... -DWITH_JPEG=ON ...

answered Mar 29, 2015 at 11:13

nils

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alitemel · Accepted Answer · 2015-03-27 09:20:20Z

0

If you want to save image with alpha channel you should use png format. It is described here

answered Mar 27, 2015 at 9:20

alitemel

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Community · Accepted Answer · 2017-05-23 12:06:08Z

0

It should work with bmp format:

cv::Mat laserSpeckle = cv::Mat::zeros(100,100,CV_8UC1);
cv::imwrite( "C://testimage.bmp", laserSpeckle );

Your code also works on my computer. However, it seems that on some systems it works only for bmp images. I saw similar issues reported here and here.

edited May 23, 2017 at 12:06

CommunityBot

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answered Mar 27, 2015 at 0:49

Amin Suzani

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Cyborg · Accepted Answer · 2017-05-26 09:46:44Z

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The problem is with the debugger version (x64) if you build the code using the release version (x64) it works fine for me.

answered May 26, 2017 at 9:46

Cyborg

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Roman · Accepted Answer · 2019-09-19 14:49:34Z

0

In my case c++ Code Generation settings were wrong Should have been Multithreaded DEBUG dll MD

answered Sep 19, 2019 at 14:49

Roman

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