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Author Topic: Automated uniform resizing of images.  (Read 4492 times)

Robslewisjr

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Automated uniform resizing of images.
« on: June 29, 2015, 12:43:32 pm »

Hello, I am trying to find a way in PS or another program or an action that will allow me to process my images from bridge so images from 10 meg upto 30 meg will process and be saved all at a final size of 4 meg, or what ever size I choose. Anyone know of a way to do this?

Thanks.
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mlewis

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Re: Automated uniform resizing of images.
« Reply #1 on: June 30, 2015, 09:14:35 am »

I'm pretty sure in the export dialog of Lightroom you can specify a target filesize. I think you can in Photoshop as well.  If so an using an action for a batch process work work for you.
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Petrus

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Re: Automated uniform resizing of images.
« Reply #2 on: June 30, 2015, 10:00:02 am »

Forgive me for asking, but what is the idea of processing all the pictures to the same file size? Same pixel dimensions and/or same JPEG compression I would understand, but the file size depends on the content of the image also. If you are setting the pixel dimension the same the pictures with most detail will be compressed more than those with less detail.
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jerryrock

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Re: Automated uniform resizing of images.
« Reply #3 on: June 30, 2015, 10:45:55 am »

Bridge/Tools/Photoshop/Image Processor
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Gerald J Skrocki

Robslewisjr

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Re: Automated uniform resizing of images.
« Reply #4 on: July 02, 2015, 11:29:16 am »

I will attempt to explain more.

I have 1000 images. I am required to upload them to an FTP site into a specific folder. The images must be within a parameter of no less than 3 meg but not over 6 meg in size. PS image processor is a "dumb" processor. It is not meant to do much else other than resize all the images and "you get what you get" when it is done. You can not ask image processor to resize files to with in a range. Lets say some files are 21 meg and if you set image processor to level 10 jpeg it will come out to 1.51 meg in this case. That is too small. It needs to be 3 meg to 6 meg. So I run it at level 12 and it comes out as 4.33 meg. That's perfect. Now I realize each image will have different color information making each image come out to different sizes. That is why I am looking for a plugin that can read the image file prior to processing and choose the compression level that will keep the final file size within my range.

Anyone ever heard of a plugin or stand alone program that can do that?

Thanks.
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Bart_van_der_Wolf

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Re: Automated uniform resizing of images.
« Reply #5 on: July 02, 2015, 12:14:29 pm »

Anyone ever heard of a plugin or stand alone program that can do that?

Hi,

JPEGs, since they will compress to varying degrees depending on image content, require an (automated) iterative approach to determine the required compression level and quality. ImageMagick allows to do that, and offers very good (user selectable) downsampling quality and scripting.

A (free) stand-alone application (Windows) tht allows to do what you are looking for (in batches), would be 'RIOT'.

Cheers,
Bart
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Robslewisjr

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Re: Automated uniform resizing of images.
« Reply #6 on: July 03, 2015, 10:42:53 am »

Thanks for the links. I tried both and unfortunately neither has the feature I am looking for. RIOT came close but will only saves JPEG images at 72dpi. My images need to be 300dpi.

If anyone else has knowledge of another program or plugin that lets you choose the dpi that would be great.

Thanks, Rob
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Redcrown

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Re: Automated uniform resizing of images.
« Reply #7 on: July 03, 2015, 12:06:16 pm »

Robslewisjr,

Please tell us who is requiring you to submit images between 3mb and 6mb at 300dpi. Such requirements are a demonstration of a severe lack of understanding of digital image processing and image quality.

Give us their full identity and contact info. We will rally the troops and descend on them with the wrath of Thomas Knoll. Or maybe we can sick our digitaldog on them. Either way, it would be much better and probably easier to show them the way than to find a processing utility that does what they foolishly ask.
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Bart_van_der_Wolf

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Re: Automated uniform resizing of images.
« Reply #8 on: July 03, 2015, 12:09:23 pm »

Thanks for the links. I tried both and unfortunately neither has the feature I am looking for.

Hi Rob,

ImageMagick has more features than most programs, maybe you overlooked the ones you are looking for (like the -define jpeg:extent={size} option for writing JPEG with a maximum file size). Filesize and image size are different things!

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RIOT came close but will only saves JPEG images at 72dpi. My images need to be 300dpi.

DPI is meaningless, except for a few antiquated workflows. The DPI (actually it's PPI, Pixels per Inch) tag is just that, a tag, which is ignored by most programs because what ultimately matters is the number of pixels in the image, and the number of inches they need to spread over (which varies with physical output size). Epson printers require 360 PPI input by default if one is to avoid low quality printer driver resampling, and Canon/HP printers require 300 PPI by default for the same output size. So the same image would be printed at different sizes if the PPI tag was followed, which makes little sense if the output media has a fixed size. Similar things happen when displayed on a monitor/display. At 100% zoom each pixel is displayed for each R/G/B 'dot'. The actual DPI for displays varies a lot, and thus the physical output sizes are all different at 100% zoom, and will need to be resampled to fit the full width or height.

Besides, RIOT just uses the PPI setting that was tagged with the original file, and ImageMagick allows to change it from whatever it was to something else (with the Density option).

Cheers,
Bart
« Last Edit: July 03, 2015, 12:19:00 pm by BartvanderWolf »
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Alan Klein

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Re: Automated uniform resizing of images.
« Reply #9 on: July 03, 2015, 12:38:42 pm »

Irfanview is free on the internet.  You can batch process size, renaming files, and all kinds of other batch changes. 

Alan Klein

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Re: Automated uniform resizing of images.
« Reply #10 on: July 03, 2015, 12:41:25 pm »

Irfan also has plugins that you should load.  It's great program for quick looking, and quick changes of things when you don't want to open your regular post processing program from Windows.

Robslewisjr

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Re: Automated uniform resizing of images.
« Reply #11 on: July 03, 2015, 01:06:28 pm »

Actually, DPI is everything in the printing process.

An image at 4000x2000@72DPI has an actual print size that will be tiny.

An image at 4000x2000@300dpi will print at actual size.

My Canon 6D's produce an image size of 5089x3393@300dpi natively. That equals a print size of 11.31x16.963inches@300dpi.

Now imagine that same image printed at a print size and dpi of 11.31x16.963@72dpi. The print resolution would be horrible at 11.31x16.963inches@72dpi but would look fine printed at its actual print size of 2.713x4.07inches. But I need a printing resolution much larger than that. So you can see that dpi is everything when it comes to an actual physical print.

The best example I can give is a web image @72dpi will print the size of a postage stamp.

Of course if you are talking only on screen resolution than you are correct, dpi means nothing.

So I think you are reading something into my post I didn't intend. Regardless I was able to discover that LR will do the job I need (close anyway). I just don't care for LR and wanted to avoid it but I guess I am stuck with it.
« Last Edit: July 03, 2015, 01:09:00 pm by Robslewisjr »
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Bart_van_der_Wolf

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Re: Automated uniform resizing of images.
« Reply #12 on: July 03, 2015, 02:53:59 pm »

Actually, DPI is everything in the printing process.

An image at 4000x2000@72DPI has an actual print size that will be tiny.

DPI is about resizing to a destination dot or line raster screen (which has a given number of dots or lines per inch). It has nothing to do with the number of pixels in the file, only the destination rasterizing parameters.

As I said, an antiquated workflow, like for traditional press, is stuck in old concepts. Modern pre-press workflows do understand the difference, because they start with pixels, then define the required output size, divide number of pixels by output size in e.g. inches (or centimeters) and the result is the resampling factor for a given destination (without the destination parameters the DPI is useless and superfluous info in an original data image, that's why often just 72 PPI is put in the tag field placeholder). When the output size is not defined as inches or centimeters, it is just a conversion to the same dimension in output dots/lines/pica's whatever one is comfortable with.

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An image at 4000x2000@300dpi will print at actual size.

No it won't. A 4000x2000 pixel image is dimensionless until the physical output dimensions are assigned, and after resampling is done. Try printing a 4000x2000 pixel image as a newspaper image, and try printing it as a high quality glossy. Both use different output screening settings, requiring different resampling to achieve the same physical output size.

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My Canon 6D's produce an image size of 5089x3393@300dpi natively. That equals a print size of 11.31x16.963inches@300dpi.

It doesn't produce an image at any physical size, it is dimensionless until one specifies how large a pixel is to become in output. 5089x3393 is dimensionless, the 300 PPI(!) is a tag which can be set to anything (it's a preference in Canon's DPP converter). Changing the PPI tag, doesn't resize the image, it remains 5089x3393 pixels. All that the tag does is say that IF the image is printed at an output size of 300 pixels per inch, it will measure 5089 / 300 PPI = 16.9633 inch by 3393 / 300 PPI = 11.31 inch.

Quote
Now imagine that same image printed at a print size and dpi of 11.31x16.963@72dpi. The print resolution would be horrible at 11.31x16.963inches@72dpi but would look fine printed at its actual print size of 2.713x4.07inches. But I need a printing resolution much larger than that. So you can see that dpi is everything when it comes to an actual physical print.

Sorry, that's not what happens. It might if you resample the image to fewer pixels, but 5089 pixels / 4.07 inches = 1250 pixels / inch (PPI, the acronym says it all, pixels per inch). Dots have nothing to do with it, unless the output screen has dots. If it has raster lines then it would be LPI. Likewise, 3393 pixels / 2.713 inch = 1251 pixels / inch PPI.

Photoshop's resize function allows to change the PPI tag, and either resample the image, or not. In fact, it also may change the value that the user puts in the PPI field without telling, and that value will get saved. It can only be detected if the image is reloaded in the resize dialog, and it may now be different, caused by imprecise rounding.

Lightroom typically resizes for an output dimension in a physical dimension, like inches or centimeters. That's why that dialog is called Resolution and it is in PPI, not DPI because it can't know what raster screen resolution (in DPI or LPI, or LPC) it will be printed on.

Cheers,
Bart
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Robslewisjr

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Re: Automated uniform resizing of images.
« Reply #13 on: July 03, 2015, 03:00:00 pm »

Bart, what I posted is all accurate and correct. What you posted is not. But we will part ways agreeing to disagree. I stopped having this argument with newbies years and years ago. Same with the cropped sensor argument. Some misunderstandings just never seem to die. But honestly, good light to you. I mean that.

Sincerly,

Rob
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