CODEWITHSUNDEEP
c#imageresolution
Mario
Mario

Reputation: 14800

How to calculate resolution based on megapixels and aspect ratio

How can I calculate in C# the exact resolution based on megapixels?

Let's say I have a 5000x4000 pixels image and I want to rescale to 0.6mpx, how can I get the exact horizontal and vertical resolution to get an image of 0.6mpx keeping the original aspect ratio?

I have this:

int nXPixels=5000;  // original image Width
int nYPixels=4000;  // original image Height
float fRatio=5000/4000;    // original image aspect ratio
int nNewPixelResolution=600000; // 0.6mpx new resolution

int nNewXPixels=?
int nNewYPixels=?

Upvotes: 0

Views: 919

Answers (2)

Chris Walsh
Chris Walsh

Reputation: 3523

int nXPixels=5000;  // original image Width
int nYPixels=4000;  // original image Height
//float fRatio=5000/4000;    // original image aspect ratio
int nNewPixelResolution=600000; // 0.6mpx new resolution
int nOldPixelResolution=nXPixels*nYPixels;
double conv = Math.sqrt((double)nNewPixelResolution/(double)nOldPixelResolution);
int nNewXPixels= (int)Math.round(nXPixels*conv);
int nNewYPixels= (int)Math.round(nYPixels*conv);

Upvotes: 2

Alex Barac
Alex Barac

Reputation: 633

Amount of megapixels is equal to the product of the length and width of the resolution, divided by 1 million. So for your 5000x4000 pixels, you would have 20 Mpx. To rescale it to 0.6Mpx, but keeping the ratio, you would just need to rescale each dimension by the squareroot of 20Mpx/0.6Mpx, so that, when the newly computed dimensions will be multiplied, the result would be equal to 0.6Mpx

So your computation should be similar to : 

ratio=sqrt(20/0.6)
newWidth=oldWidth/ratio
newHeight=oldHeight/ratio

If you then multiply newWidth with newHeight, the result should be aproximately 0.6Mpx, or 600000 px

Upvotes: 3

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