Here are a few thoughts to keep in mind when posting images to Digital-DIY.
Your computer screen probably has 1280 pixels across the width or more. A pixel is the smallest dot that can be displayed on the screen. To effectively read a plain text font, the character size has to be at least 5 pixels by 7 pixels.
Pictures Posted in a Forum
Pictures posted in a forum are scaled down to about 670 pixels wide; smaller pictures are displayed at full size. Ideally, pictures should be readable when scaled to a width of 670 pixels.
If a picture has been scaled down, clicking on it will scale it to the maximum size that will fit on the screen (proportional, limited by height and width. Not all forums are the same in this regard. A safe assumption is that a maximum size of about 1100 x 800 pixels will be displayed depending on the user's computer.
If a picture is copied or saved using a right mouse click, it will be available to another program at full resolution.
So, as a general rule, an image will be readable with a width of about 670 pixels for people to be able to view it in the forums. At the outside, the image should be viewable at a size of about 1000 x 800 pixels so people can view it by clicking on it. If the image is not clear at these sizes, consider other means of sharing it, like a pdf.
Maximizing Image Clarity
It goes without saying that every pixel needs to count in order to make a schematic or other image clear with a width of 670 pixels! How do we make the most out of the pixels we have available?
The image below is a simple schematic and was saved at a resolution of 1495x1060. It's a bit difficult to make out the details but a bit better if clicked to zoom in.
Compare this to the image below. The detail is clear because the image has been cropped to remove unnecessary white space.
In this case, it's pretty clear that unnecessary space was included in the first schematic because there's a frame around the space. Sometimes programs will copy an entire page area in a graphic even though most of the space is unused. That's what's happened below. Note that the uploaded image fills the screen - most of it's blank.
The same information is in all three schematics at the same resolution. Because of the way images are scaled for display. one is very clear, one is ok and one is unreadable.
The maximum size for viewing on the screen is between 670 and about 1100 pixels. We've just seen that we need to focus in on the area of concern and reduce the wasted space. The other side of the coin is how much information we can put in this space. The information on the original image needs to fit into the space we have.
Most schematic capture and PCB layout programs have an option to export an image and give you some way to scale the output. In TinyCad, it's a scale factor, in Eagle, it's in terms of dots-per-inch resolution.
You need to adjust the image size to yield about 1000 pixels wide in the area of interest. If you don't have enough resolution, you can't "fix it later."
the image below is a PCB exported from Eagle at too low a resolution and expanded up to the desired size. It makes me dizzy.
Here's the same board saved with a resolution that made the final size about 1200 pixels wide. It's scaled down a bit for viewing here, but it's sharp and clear.
The images displayed in the forum here are about 670 pixels wide and can be expanded to about 1200 wide. If your image isn't clear when displayed at that size, you'll need a different way to share it.
The use of the limited number of pixels needs to be maximized to display images clearly. Crop the image if your software is including more than the area of interest in the exported image.
Export the image file with enough resolution to fill the screen. Expanding a small image to fit the screen makes blurry images.
Please look at your images after you post them. If they are not clear, edit the post and fix the images. If you can't read it, why should anybody else be expected to?
Here's an example of an image bordering on too big to display as an image - the schematic of my sous vide board. The original image is about 4500 pixels wide but it's displayed here scaled to around 670 pixels or around 1100 if you click on it.
This is about the maximum level of detail that can be made out here. As explained above, the image may be copied or downloaded and displayed at full size in another program. but this is inconvenient.
If you'd like to post an image file with more detail, the next option is to create an Acrobat PDF file. The detail will be preserved in this standard format file.
There are many image manipulation programs available that can make images work for you. I've found Irfanview to be powerful and easy to use.
There are also a number of programs to create Acrobat files - you're not limited to Adobe Acrobat Writer. PrimoPDF is one I've found to work well. Primo installs a special print driver. Creating a PDF is an simple as printing the document and selecting PrimoPDF as the printer.
It generally doesn't work too well to share files in proprietary file formats. IF you post a DIPTrace file, an Eagle file, a TinyCAD file or even a Microsoft Word document, it instantly limits the number of people who can access the file.
The exception to this is Gerber files / Excellon drill files. These are the standard files for having boards made.
Re: Information About Posting Images on Digital-DIY
7 years 1 week ago #11092