CODEWITHSUNDEEP
iosimage-processing
scorpiozj
scorpiozj

Reputation: 2687

compress UIImage but keep size

I try to use UIImageView to show the photo. But the Photo sometimes is a little large, and I want to compress it.But I'd like to keep its size. For example,a photo is 4M and has a size of 320X480. And I want to compress it and it may have 1M but still has a size of 320X480.

thanks!

Upvotes: 3

Views: 10059

Answers (2)

Henry95
Henry95

Reputation: 623

If your goal is to get the image below a specific data length, it's tough to guess what compression ratio you need, unless you know the source image will always be a certain data length. Here's a simple iterative approach that uses jpeg compression to achieve a target length... let's say 1MB, to match the question:

// sourceImage is whatever image you're starting with

NSData *imageData = [[NSData alloc] init];
for (float compression = 1.0; compression >= 0.0; compression -= .1) {
    imageData = UIImageJPEGRepresentation(sourceImage, compression);
    NSInteger imageLength = imageData.length;
    if (imageLength < 1000000) {
        break;
    }
}
UIImage *finalImage = [UIImage imageWithData:imageData];

I've seen some approaches that use a while loop to compresses the image by .9 or whatever until the target size is met, but I think you'd be losing image quality and processor cycles by successively compressing/reconstituting the image. Also, the for loop here is a little safer because it stops automatically after trying the maximum possible compression (zero).

Upvotes: 3

AliSoftware
AliSoftware

Reputation: 32681

Compress it using the JPEG compression.

lowResImage = [UIImage imageWithData:UIImageJPEGRepresentation(highResImage, quality)];

Where quality is between 0.0 and 1.0

You should read the UIImage documentation, everything is explained in there…

Upvotes: 18

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