I am trying to just change the resolution of a tiff image using Bit Miracle libtiff. Below is the code snippet. When I do this, tiff image resolution is changed, but the other tiff parameters are gone and I am unable to open the tiff file. Could you please help if I am doing something wrong here?
using (Tiff image = Tiff.Open(fileName, "a"))
{
image.SetField(TiffTag.XRESOLUTION, 200);
image.SetField(TiffTag.YRESOLUTION, 300);
image.WriteDirectory();
}
Please note that changing TiffTag.XRESOLUTION or TiffTag.YRESOLUTION won't change image data and will only change the way the data is interpreted by viewers or printers.
As for the code itself, you should:
Call SetDirectory(0) before calling SetField methods. That's because you open file in append mode.
Use RewriteDirectory instead of WriteDirectory. Otherwise you might corrupt image data.
Related
I created a delphi component and want to load an image into it at runtime.
So i created a .RC file in notepad.
useIdentifer BITMAP "demo.BMP"
When i compiled the file it gave me an error "invalid bitmap format", so I did some research and got the solution that I had to check that the file is 8-bit, so I converted it to bitmap 256 colors using paint, but due to this i lost the quality and pixels of image.
I'm not sure how can i get rid of the error without losing quality of the image.
Use a PNG image instead of a BMP. The answer to this question will tell you how.
The image http://www.barre.nom.fr/medical/samples/files/MR-MONO2-16-head.gz on http://www.barre.nom.fr/medical/samples/is not converting to other image formats. I tried following commands (after extracting the dicom file):
dcm2pnm --write-png MR-MONO2-16-head out.png
dcm2pnm +obr MR-MONO2-16-head out.bmp
dcm2pnm MR-MONO2-16-head out.pnm
It also did not work with dcmj2pnm and dcml2pnm. All of them just produce a gray box. The image otherwise is OK and is correctly read by proper dicom viewer softwares. Where is the problem and how can it be solved?
The problem is that no windowing settings are present in the header. You need to instruct dcm2pnm to calculate a window from the histogram (+Wm) or specify windowing values to apply.
dcm2pnm +Wm +obr MR-MONO2-16-head MR-MONO2-16-head.bmp
yields a bitmap image that looks fine to me.
I am using OpenCV 3.0 and whenever I read an image and write it back the result is a washed-out image.
code:
cv::Mat img = cv::imread("dir/frogImage.jpg",-1);
cv::imwrite("dir/result.jpg",img);
Does anyone know whats causing this?
Original:
Result:
You can try to increase the compression quality parameter as shown in OpenCV Documentation of cv::imwrite :
cv::Mat img = cv::imread("dir/frogImage.jpg",-1);
std::vector<int> compression_params;
compression_params.push_back(CV_IMWRITE_JPEG_QUALITY);
compression_params.push_back(100);
cv::imwrite("dir/result.jpg",img, compression_params);
Without specifying the compression quality manually, quality of 95% will be applied.
but 1. you don't know what jpeg compression quality your original image had (so maybe you might increase the image size) and 2. it will (afaik) still introduce additional minor artifacts, because after all it is a lossy compression method.
UPDATE your problem seems to be not because of compression artifacts but because of an image with Adobe RGB 1998 color format. OpenCV interprets the color values as they are, but instead it should scale the color values to fit the "real" RGB color space. Browser and some image viewers do apply the color format correctly, while others don't (e.g. irfanView). I used GIMP to verify. Using GIMP you can decide on startup how to interpret the color values by format, either getting your desired or your "washed out" image.
OpenCV definitely doesn't care about such things, since it's not a photo editing library, so neither on reading nor on writing, color format will be handled.
This is because you are saving the image as JPG. When doing this the OpenCV will compress the image.
try to save it as PNG or BMP and no difference will be exist.
However, the IMPORTANT QUESTION : I am loading the image as jpg and saving it as JPG. So, how there is a difference?!
Yes, this is because there is many not identical compression/decompression algorithms for JPG.
if you want to get into some details see this question:
Reading jpg file in OpenCV vs C# Bitmap
EDIT:
You can see what I mean exactly here:
auto bmp(cv::imread("c:/Testing/stack.bmp"));
cv::imwrite("c:/Testing/stack_OpenCV.jpg", bmp);
auto jpg_opencv(cv::imread("c:/Testing/stack_OpenCV.jpg"));
auto jpg_mspaint(cv::imread("c:/Testing/stack_mspaint.jpg"));
cv::imwrite("c:/Testing/stack_mspaint_opencv.jpg", jpg_mspaint);
jpg_mspaint=(cv::imread("c:/Testing/stack_mspaint_opencv.jpg"));
cv::Mat jpg_diff;
cv::absdiff(jpg_mspaint, jpg_opencv, jpg_diff);
std::cout << cv::mean(jpg_diff);
The Result:
[0.576938, 0.466718, 0.495106, 0]
As #Micha commented:
cv::Mat img = cv::imread("dir/frogImage.jpg",-1);
cv::imwrite("dir/result.bmp",img);
I was always annoyed when mspaint.exe did the same to jpeg images. Especially for the screenshots...it ruined them everytime.
How do I write a valid tiff image in python with my own data for the tiff file?
I've tried doing a few things using PIL and it's not a valid image.
If you could answer with some sample code of making a tiff image then editing the data using PIL that would be more than enough and go a long way in moving my program along
Are you required to exactly use PIL? Otherwise, have you tried using it's open source clone called Pillow? Refer to https://python-pillow.github.io/
Pillow seems to be able to directly save image data in tiff file format.
Try something like:
img = Image()
# any editing of 'img'
img.save( 'mytiff.tif' )
Otherwise, you should clarify your needs or problems in depth.
I have unpickled an image, and utilizing PIL when I use img.show() I can see the image in external viewer properly but when I try to save it using img.save() it is plagued by horizontal color artifacts. As img.show() is using bmp to temporarily save and show the file, I tried using img.save(filepath, "bmp") as well as other file formats. Other formats, such as jpg and png, totally corrupt the image, while bmp creates color artifacts. I checked the documentation for PIL but it was not helpful. What method can I use to save the image I see properly?
After many tries, it turns out instead of:
with open("img.bmp", 'w') as f:
image.save(f)
opening the file with the binary attribute "b" added solves the issue. Like this:
with open("img.bmp", 'wb') as f:
image.save(f)