inch

Question

hi, just want to ask if how many pixels in 1 inch of an image? is there a specific value for this like 72 pixels is equal to 1 inch for all images? thanks

franches · Answer

i hve posted the raster image map at www.webshots.com. the username is harrha202 and password ils harrha. hope you'll test my code to see what i mean. thank you very much.

franches · Answer

i found these about raster image: Raster images consist of a grid, or raster, of small squares or pixels. Raster images are resolution-dependent and appear jagged, fuzzy and lose detail if they are scanned or created at a low resolution and are then printed at a high resolution. Raster images are already described as a series of dots.

franches · Answer

i have backgrounds in programming when i was in college. visual C# is new to me, i am now a trainee. i am learning visual c# as a self-study and also with guides of the forum. i am asking the forum since i really am having hard time with the dpi. while asking the forum i am reading some books. i am not a fast learner so i have to read books that are easily to understand and sometimes learn from people who have the knowledge. i have two image which are both maps. the photo image map are images taken by camera and etc. while the raster image map are only black and white, it's like a drawing or sketch map. i really can't describe or explain about raster image. if you want i can email you sample of a raster image.

McCarthy · Answer

Well, if you were instructed, it sounds like homework, which means you aren't really learning anything if you are asking someone else to figure out the problem for you... and DPI is not what you are interested in, DPI is dots per inch and that is a printing term... unfortunately lots of programs confuse the difference between DPI and PPI. I don't know what you mean by raster vs. photo image... there are only two real types of images, raster (pixels), and vector (points joined by geometry)... so I don't see how photo makes a differece.

franches · Answer

actually, i was instructed to make a form which load an image. after loading the image it should display in 3 textboxes. image width, height and dpi. i was able to display the image width and height but cant display the dpi. i am not sure if i am doing the right thing if the dpi is the h/v resolution. i am wondering why is it that my raster image has 0,0 h/v resolution while my photo image has 1239,1239 h/v resolution.

McCarthy · Answer

If you go into photoshop and go to Image Size, you will see the height + width in pixels and then the PPI ~ pixels per inch... if you change the pixels per inch to a higher values your PPI will change to a higher value as well... Similarly, if you save one image as 300 PPI, and then load it back into photoshop and change the dpi back down to 72 it will adjust the image size to a smaller PPI... This shouldnt do this with a photoshop or tiff or eps... what I'm getting at is that I don't know what you will get from software trying to get the H/V resolution as most software is different when it comes to DPI vs PPI... I do know that all software that displays images should display them on screen the same if they were saved as 72 or 300 dpi or whathaveyou... that number shouldn't effect how an image displays on screen, but it may effect what values your code gives you, I havent tried it... I did try it in photoshop and what I expected was true, the images displayed with the same sizing in relationship to the screen resolution. What are you trying to do and maybe I can be more helpful.

franches · Answer

thanks for your response. Image image = Image.FromFile(openFileDialog.FileName); float w =image.HorizontalResolution; string ww = Convert.ToString(w); float v =image.VerticalResolution; string vv = Convert.ToString(v); textBox11.AppendText(ww + "," + vv); int x = image.Size.Width; string xw = Convert.ToString(x); int y = image.Size.Height; string yh = Convert.ToString(y); textBox2.AppendText(xw); textBox3.AppendText(yh); with this code, if i opened the image which is raster image the horizontal resolution and vertical resolution is 0,0 while the photo image is 1269,1269. when i opened the 2 images in photoshop elements. i checked the image size and i noticed the resolution of the raster image is 72 pixels/inch and the photo image is 1269 pixels/inch. this is why i asked how many pixels in an inch of any images so that i would compute it instead of calling it (float w =image.HorizontalResolution. or do you have any solutions for my problem? or is there any formula on how to convert from pixels to inch?

McCarthy · Answer

The number of pixels per inch is never used in designing an interface, the relationship of pixels per inch / dots per inch only matters in printing. However, you should make sure that either your form as controls to re-scale itself to different resolutions... Second, there is probably no way around the fact that a window will look huge at 640x480, and not so huge at 1280x1024, last, there isn't even a way to effectively measure something arbitrary like an inch due to the different curves of crts/flatscreens/lcds... Hope that helps. Many times when I have a client who says "how do I?", I have to ask them what they want to accomplish, before I get to the business of telling them how to do it, or if what they want to do is even necissary... Writing any code is a lot like that.

jcity444 · Answer

Resolutions can vary. You should get your horizontal and vertical resolution from your system. The code below will give you the number of pixels/inch for each dimension when placed in your form (for a windows form application). -Mike G. public Form1() { // // Required for Windows Form Designer support // InitializeComponent(); Graphics g = CreateGraphics(); float horizontalResolution = g.DpiX; float verticalResolution = g.DpiX; Console.WriteLine("Horizontal Resolution = {0}, Vertical Resolution = {1}", horizontalResolution, verticalResolution); // // TODO: Add any constructor code after InitializeComponent call // }