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Will the image resolution ratio change when I change the image attribute width or scale?

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Will the image resolution ratio change when I change the image attribute width or scale?

Dear all,

We konw that the dpi basically is used to calculate the print size of a given image. When we change the image resolution ratio, for example, from 96dpi to 200dpi, when I pubish the PDF document, the size of the image are different. The 200dpi's is larger.

Then I have some questions:

1. When I publish the PDF, did the the image resolution ratio change? If changed, how much has changed? I'm not sure if some problem in my understanding of basic concepts.But I print the PDF and office word document for the image, I think the image in word document is clearer.

2.When I change the image attribute width or scale, the size of the image will change also. Did the the image resolution ratio change? Can I control the dpi by these attribute, how?

3.The custom want the image resolution ratio in PDF is 200dpi, and also want a width 70mm, is this possible? How can I achieve it? I don't h

4. By the way, this is for PDF, how about for RTF, Web, or html?

Could you give me any tips please? Your assistance will be highly appreciated in this regard.

Thanking you!

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Will the image resolution ratio change when I change the image attribute width or scale?

A lot of questions there I'll address the DPI concerns. Presumably you are aware DPI is "dots per inch" from the old print days meaning how many dots of ink fit in one inch. For computers, DPI means "pixels per inch" so you will sometimes see PPI written.

On to your example. The original image is typically a bitmap format (JPEG, PNG, GIF, etc.) which may or may not have DPI information attached. It will however know exactly how many pixels it has e.g. 1500x1000.

The output image is governed by the formatting system (Arbortext in this case). You can set the desired DPI and Arbortext will ensure the image matches that DPI. If the source DPI is lower than the target DPI then your image may show poorly.

For customer's image of 200dpi at 70mm width you can calculate easily the required source image dimensions.

1. 70mm = ~2.756 in (1 in = 25.4 mm)

2. 2.756 in x 200 dots = 551.2 dots (round up to 552)

3. Source image must have 552 pixels horizontally

So for the example if your image has 552 pixels or greater then it can be downsized to fit into 70mm. If it has less than 552 pixels it must be upsized to fit into 70mm. Upscaling will cause a poor looking image. Downscaling usually produces an acceptable image (assuming a modern resampling algorithm is used).

2 REPLIES 2

Re: Will the image resolution ratio change when I change the image attribute width or scale?

A lot of questions there I'll address the DPI concerns. Presumably you are aware DPI is "dots per inch" from the old print days meaning how many dots of ink fit in one inch. For computers, DPI means "pixels per inch" so you will sometimes see PPI written.

On to your example. The original image is typically a bitmap format (JPEG, PNG, GIF, etc.) which may or may not have DPI information attached. It will however know exactly how many pixels it has e.g. 1500x1000.

The output image is governed by the formatting system (Arbortext in this case). You can set the desired DPI and Arbortext will ensure the image matches that DPI. If the source DPI is lower than the target DPI then your image may show poorly.

For customer's image of 200dpi at 70mm width you can calculate easily the required source image dimensions.

1. 70mm = ~2.756 in (1 in = 25.4 mm)

2. 2.756 in x 200 dots = 551.2 dots (round up to 552)

3. Source image must have 552 pixels horizontally

So for the example if your image has 552 pixels or greater then it can be downsized to fit into 70mm. If it has less than 552 pixels it must be upsized to fit into 70mm. Upscaling will cause a poor looking image. Downscaling usually produces an acceptable image (assuming a modern resampling algorithm is used).

Highlighted

Re: Will the image resolution ratio change when I change the image attribute width or scale?

Thank you, Gareth!

You answer the perfect solution to my problem