iPhone：创建视频缩略图 [英] iPhone: Create video thumbnail

问题描述

如何使用UIImagePickerController didFinishPickingMediaWithInfo提供的信息创建缩略图？

How can I create a thumbnail image from info provided by UIImagePickerController didFinishPickingMediaWithInfo?

推荐答案

static inline double radians (double degrees) {
    return degrees * M_PI/180;
}

- (UIImage*) imageByScalingToSize:(CGSize)targetSize image:(UIImage*)image {
    UIImage* sourceImage = image;
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;

    CGFloat sourceHeight = image.size.height;
    CGFloat sourceWidth = image.size.width;

    if(sourceHeight < sourceWidth) {
        CGFloat ratio = sourceWidth/sourceHeight;
        targetWidth = ratio*targetHeight;
    }else if(sourceHeight > sourceWidth) {
        CGFloat ratio = sourceHeight/sourceWidth;
        targetHeight = ratio*targetWidth;
    }

    CGImageRef imageRef = [sourceImage CGImage];
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);

    if (bitmapInfo == kCGImageAlphaNone) {
        bitmapInfo = kCGImageAlphaNoneSkipLast;
    }

    CGContextRef bitmap;
    if(sourceImage.imageOrientation == UIImageOrientationRight) {
        float temp = targetWidth;
        targetWidth = targetHeight;
        targetHeight = temp;
    }

    if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
        bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
    } else {
        bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
    }

    if (sourceImage.imageOrientation == UIImageOrientationLeft) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);
    } else if (sourceImage.imageOrientation == UIImageOrientationRight) {
        CGContextRotateCTM (bitmap, radians(-90));
        CGContextTranslateCTM (bitmap, -targetWidth, 0);
    } else if (sourceImage.imageOrientation == UIImageOrientationUp) {
        // NOTHING
    } else if (sourceImage.imageOrientation == UIImageOrientationDown) {
        CGContextTranslateCTM (bitmap, targetWidth, targetHeight);
        CGContextRotateCTM (bitmap, radians(-180.));
    }

    CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage *newImage1 = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return newImage1;
}

只要传递要创建缩略图的大小即可。

just pass size of which you want to create thumb image.

这篇关于iPhone：创建视频缩略图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！