This appears to be a trivial problem but the result is strange, totally lost where I am going wrong. There is an input RGB image which needs to be converted to gray scale and sized to 1000 x 1000 pixels. This is how I have done
img=imread('flowers.jpg');
flowers_gray=rgb2gray(img);
flowers_resize=imresize(flowers_gray,[1000 1000]);
but strangely the output image is not of 1000 by 1000 pixels. Moreover, matlab did not save the image (tried using SaveAs option and the File --->Export Setup) gray scale mode
and also the size was incorrect since when I opened the saved image by
img1=imread('flowers_resize.jpg')
s=size(img1)
it gave
s=586 665 3
And the image flowers_resize.jpg is saved with a white border surrounding it in the image folder. So, I went to Paint toolbox to select the image A1 and manually deleted the surrounding background and resized the image.But alas, it saved the image with 3 color channels and not in gray scale mode although the size was correct! Can somebody please point out the correct way of resizing to 1000 by 1000 pixels and saving in gray scale mode without the white border surrounding the saved output file? Thank you.
When you use the image export processing, you are saving the entire figure including the space around the figure (white space).
Instead, use the imwrite command. In your case:
imwrite(A1,'flowers_resize.jpg','jpg');
Related
I am trying to write a large image to PDF (141"x24" at 300 DPI, so 42300 pixels x 7200 pixels). I can write the image as a png without a problem using imwrite(). However, imwrite() does not provide PDF as an output option. So, the alternatives I have seen online all do something like this:
pdffig = figure;
set(pdffig,'Units','Inches','Position',[0 0 141 24],'PaperSize',[141 24]);
pdfaxs = axes;
imshow(Im,'Parent',pdfaxs);
print(pdffig,'largeimage.pdf','-dpdf');
This code is creating a figure, setting some properties to make the figure 141x24 inches in size, showing the image on the figure axis, and then printing the figure contents to pdf.
Unfortunately, what happens is that the figure is resized to fit my screen when imshow() is called and then the printed pdf will have a small version of the image in the center of a large white pdf. What I actually want is for the image to take up the entire 141"x24" pdf. I have tried rearranging when the window size is set and when imshow() is called, but that doesn't help. Note that this works if the desired PDF size fits on my screen (e.g. if I was printing a 12"x12" PDF).
Any suggestions are appreciated!
I have a problem with some dicom images. Maybe they have a different image range.
Generally it display as normal with black background but sometimes it display with white background. I have a question : what can I change it ? I would like to display images always with black background.
I would appreciate for any help/advice. I don't know what I should change ?
Agata
Please check the value of Photometric Interpretation (0028, 0004). This specifies the intended interpretation of the image pixel data. If the value is “MONOCHROME1” than the minimum sample value of pixel data is intended to be displayed as white (after any Modality LUT transformation) and maximum pixel value as black (inverted grayscale image)
I have to resize image i.e if its dimension is 3456x5184 to 700X700 as my code needs image with less number of pixels otherwise it takes too much time to give results.So, when I use imresize command it changes the dimensions of image but at the same time it changes the shape of image i.e the circle in image which I also need to detect looks like oval instead of being cirle. I need your suggestions to resolve this problem. I am really grateful to you people.
Resizing images is done by either subsampling (to get smaller images) or some kind of interpolation (to get larger images)
Input is either a factor or a final dimension for width and height.
The only way to fit a rectangle into a square by simply resizing it is to use different scales for width and height. Which of course will yield in a distorted image.
To achieve what you want you can either crop a 700x700 region from your image or resize image using the same factor for with and height. Then you can fit the larger dimension into 700 and fill the rest around the other dimension with black or whatever you prefer.
I am using an image with size 4000*3000 pixels. When I show this image through the imshow function, the program shows:
Image is too big to fit on screen : displaying at 67%.
After that, when I want to find size of the image with function size(), the number of column is always multiplied by 3 from the original image. For example, when my image is 563*1000, this function show me 563*3000.
Could anyone tell me how to fix this problem?
The original PNG image is 800x1200 and takes up about 34K. After the images is resized by GraphicsMagick to 320x480 size, the resulting images takes up approximately 37K. (For comparison, if the image is resized with Paint on Windows 7 then the resulting image is 40K.) What gives? The whole point of resizing an image was to save space. How should GraphicsMagick be used to shrink the image size?
PNG is a lossless format and compresses the image data by first performing a step called prediction and then applying the same algorithm used in zlib. The prediction step is a crucial one in order to effectively compress the file, and it is based on the values of earlier neighbors pixels.
So, suppose you have a large PNG in black & white (by that I really mean only black and white, some people confuse that by grayscale sometimes). Also suppose it is not a tiny checkerboard pattern. In many regions of this image, you will have a relatively large white region, and then a relatively large black region, and so on. When the predictor is inside one of these large regions, it has no trouble to correctly predict that the current pixel intensity is exactly equal to the last one. This makes it easier to better compress the data describing your image.
Now, let us downscale this black & white image using some resampling filter different than nearest neighbor (let's say Lanczos). This has a great chance to turn your black & white image into a grayscale one, which has a much greater intensity range. This potentially makes the job of the predictor much harder, and thus the final file size might be larger.
For instance here is a black & white 256x256 PNG image which takes 5440 bytes, a resizing of it (using 3-lobed Lanczos) to 120x120 which now takes 7658 bytes, and another resizing (using nearest neighbor) to 120x120 which occupies 2467 bytes.
PNG is a compressed format. Sometimes trying to compress a maximally compressed item actually results in a larger item. So if the 800x1200 is resized to a smaller size, but the result retains everything that was in the original, because the original is already as minimal as possible, you could see this happen. To demonstrate this, try using 7zip to compress some data with ultra compression. Then try compressing the compressed file. Often the second compressed file will be larger than the first.