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Export tiff in greyscale

 
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godsdice



Joined: 17 Oct 2017
Posts: 3

PostPosted: Tue Oct 17, 2017 11:38 am    Post subject: Export tiff in greyscale Reply with quote

Hi,

when I try to export tiff files, they always are in RGB. I would need to convert them in greyscale (non-RGB). I tried with Act on all commands > Change colors to grayscale, but it didnít work. I also tried to set the background in the canvas on nothing, but it seems that when I export the tiff files, these are automatically converted in RGB colors. Is there a way to solve this problem? The alternative would be to open every file in Photoshop, convert it and save it, but it sounds naive, and I have 99 graphs to convertÖ

Thank you for your help.
Best,
A.
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David
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Joined: 25 Nov 2006
Posts: 1940
Location: Chapel Hill, NC

PostPosted: Wed Oct 18, 2017 11:11 am    Post subject: Reply with quote

Great suggestion.

I added this to the latest beta. I added a checkbox to save the image as grayscale.

David
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godsdice



Joined: 17 Oct 2017
Posts: 3

PostPosted: Wed Oct 18, 2017 11:52 am    Post subject: Reply with quote

David wrote:
Great suggestion.

I added this to the latest beta. I added a checkbox to save the image as grayscale.

David



Thank you so much. This is very useful.

But, in effect, this way seems that the graph is in RGB colors and then converted in grayscale when exported in tiff. This provokes a loss of quality and the resulting image appears little blurry, especially if compared with the eps/RGB version.

Would it be a way to create directly a graph in grayscale/non-RGB?

My problem is that, when I export the document from indesign for printing, the graph in grayscale appears little blurry compared to the text body. And, unfortunately, my publisher doesnít accept files containing graphs in RGB colors.

Here are two examples:
https://drive.google.com/open?id=0B0gj5L9ZPvCAZ3FnWkx3Z2pOenc
https://drive.google.com/open?id=0B0gj5L9ZPvCAMWx1ZEszVnc0M2M

Thank you in any case for your kindness, as usual.
Andrea
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David
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Joined: 25 Nov 2006
Posts: 1940
Location: Chapel Hill, NC

PostPosted: Wed Oct 18, 2017 12:03 pm    Post subject: Reply with quote

It looks like Apples routines can't render directly into a grayscale, so I do create the Reb and then use the standard RGB->gray conversion.

You mean that the Gray that I make from the rgb is fuzzier than what Photoshop does? The resolution is adjustable, and the default - 72 - is standard but very low resolution. Specify a higher resolution in DG when you export the graph.

David
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David
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Location: Chapel Hill, NC

PostPosted: Wed Oct 18, 2017 12:06 pm    Post subject: Reply with quote

I would use at least 600dpi and you don't have to select the smooth option. The smooth option will add grayscale values at edges to make it look smoother.

David
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godsdice



Joined: 17 Oct 2017
Posts: 3

PostPosted: Wed Oct 18, 2017 12:37 pm    Post subject: Reply with quote

quote="David"]You mean that the Gray that I make from the rgb is fuzzier than what Photoshop does?[/quote]

No, it is quite the same. The Gray in grayscale is fuzzier than that in RGB. I think this occurs because conversion causes a loss of details (because the range of colors is reduced to a maximum of 256, I suppose). In brief, black is not as black as the text in the text body. If you look at the two pages at the links in my previous post, the text in the graph in RGB colors is as black as the text below. Not the same in the other case, with the graph in grayscale.

I used 1200 dpi, as requested by my publisher. And I unchecked the smooth option.

I donít know if this problem can be solved, actually. Probably, it would be better to have the possibility to create the graph in grayscale than to convert it from RGB. But I donít know if this is possible technically.
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David
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Location: Chapel Hill, NC

PostPosted: Wed Oct 18, 2017 4:09 pm    Post subject: Reply with quote

What I tried was to create a picture in DataGraph that only has gray values and export it as a rgb and gray.

I got exactly the same result, pixel by pixel. In the sense that the rgb image has the same value for r,g,b as the the gray value.

Now of course the rgb image is larger since it is essentially three copies of the same image, but I wanted to check to see if there was some difference in the values due to round-off or rendering artifacts the gray scale image.

It is true that each channel is typically 8 bits, so you can only have 256 different values for gray. The same holds for each component in a RGB image. If you convert the rgb image to a 16 bit grayscale image you will get more shades of gray, but for a graph you typically don't have a lot of colors. I would turn off the smoothness in the output. This will help with blending between solid areas. When you alias shapes there is often a tiny line between solid rectangles that share an edge. If you turn off smoothing there is no color fringe between them. It will also reduce the number of colors. The image will be a little jagged when you zoom down to individual pixels, but at 1200dpi that should not be visible.

The fuzzyness could also be because of how you render the image. For example how Indesign draws it. Text is handled by the OS, which uses tricks to render things sharply. Indesign might subsample the image for rendering to the screen but send the full resolution to the printer. They might also apply agressive interpolation to an image when they draw it to the screen. In the Graphic command I allow you to specify the interpolation method when you draw a bitmap. If you have continuous color images (photographs) you typically want to use high interpolation. Sometimes an image is drawn half a pixel off and that averages the neighboring pixels.

You should be able to see if the image is really blurry by zooming in on the image and see if the blurryness scales or stays at the same level of blurriness.

The best would of course be if they allow you to include the pdf image, but often publishers don't want that because of problems with fonts (slight differences between their font metrics and yours for non-embeddded fonts).

David
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