Strange error (Assertion Failed) when averaging images

[wendelscardua]

Hi, I have some old code (from 2010) that used to work (it would apply some operation on each image of a list, then average them into a final image), but on recent versions of ImageMagick I get this (internal?) error message:

Code: Select all

magick/cache-view.c:163: AcquireVirtualCacheView: Assertion `image != (Image *) ((void *)0)' failed.

(and sometimes this line show up doubled)

This is a sample of the code (ok, it's 90% of it):

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		MagickWandGenesis();

		image = NewMagickWand();

		for(a = 1; a <= samples; a++) {

			image_temp = NewMagickWand();

			sprintf(filename, "%s/%s-%02d.jpg", argv[1], argv[2], a);

			if (MagickReadImage(image_temp, filename)==MagickFalse) {
				ThrowWandException(image_temp);
			}

			width = MagickGetImageWidth(image_temp);
			height = MagickGetImageHeight(image_temp);

			pixels_gs = (unsigned char **) create_array(width, height, sizeof(char));
			pixels_gs_tmp = (unsigned char **) create_array(width, height, sizeof(char));

			for (i=0; i<height; i++) {
				MagickGetImagePixels(image_temp, 0, i, width, 1, "I", CharPixel, pixels_gs[i]);
			}

			gs_threshold(pixels_gs, width, height, 140);

			gs_erosion_viz(pixels_gs, width, height,2,1);

			for (i=0; i<height; i++) {
				MagickSetImagePixels(image_temp, 0, i, width, 1, "I", CharPixel, pixels_gs[i]);
			}

			MagickAddImage(image,image_temp);
            
			DestroyMagickWand(image_temp);

		}

		image = MagickAverageImages(image);

		MagickWriteImage(image, argv[4]);
 

The weirdest thing is: it works if I'm averaging only a single image (i.e samples == 1). And it runs if I comment the last two lines (MagickAverageImages and MagickWriteImage), so it's really the MagickAverageImages fault.

If this is happening because MagickAverageImages is deprecated... Then I'd ask what is the replacement for it, because I couldn't find it.

Thanks in advance

[fmw42]

-average is deprecated but should still work. the replacement is -evaluate-sequence mean. however, I do not know what the MagickWand version would be, since I do not use any APIs.

How many images were you trying to average and how big were they?

[wendelscardua]

How many images were you trying to average and how big were they?

50 images. Each image is 5k in size, 180x60 jpegs. But it fails even for 2 of these, so it's not a size issue.

[el_supremo]

In place of

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imagem = MagickAverageImages(imagem);

try

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imagem = MagickEvaluateImages(imagem,MeanEvaluateOperator);

But I think it is a mistake to overwrite imagem with the new image. You would be better off to declare another MagickWand and do this sort of thing:

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MagickWand *mw;
mw = MagickEvaluateImages(imagem,MeanEvaluateOperator);
DestroyMagickWand(imagem);
MagickWriteImage(mw, argv[4]);
DestroyMagickWand(mw);

Pete

[wendelscardua]

Thanks for the replacement, but although it solved the "deprecated" warning, the "Assertion Failed" error still happens.

(I wrote it the way you suggested)

[wendelscardua]

PS: after that, I got rid of all deprecations warnings (replaced Magick{Get,Set}ImagePixels with Magick{Export,Import}ImagePixels), the "assertion failed" keeps happening.

Also, forgot to say what version I'm using. I'm on Ubuntu 12.04, and according to synaptic the version installed is "8:6.7.7.10-2ubuntu4".

[el_supremo]

Before MagickEvaluateImages add this:

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MagickResetIterator(imagem);

Pete

[wendelscardua]

Thanks! That was it...