各类型图片转data

            CDPhotoAssets *asset = _imageArray[i];
            UIImage *finalImage = [asset originImage];
            ALAssetRepresentation *representation =[asset.asset defaultRepresentation]; //ALAssetRepresentation已过期,Use PHImageRequestOptions with the PHImageManager from the Photos framework
            NSString *imageName = [representation filename];
            NSArray *type = [[representation filename] componentsSeparatedByString:@"."];
            NSData *data = [CDFeedbackViewController compressImage:finalImage toByte:1024*1024];
            if ([type.lastObject isEqualToString:@"GIF"] || [type.lastObject isEqualToString:@"gif"]) {
                Byte *imageBuffer = (Byte *)malloc(representation.size);
                NSUInteger bufferSize = [representation getBytes:imageBuffer fromOffset:0.0 length:representation.size error:nil];
                data = [NSData dataWithBytesNoCopy:imageBuffer length:bufferSize freeWhenDone:YES];
            }else if ([type.lastObject isEqualToString:@"png"] || [type.lastObject isEqualToString:@"PNG"]){
                data = UIImagePNGRepresentation(finalImage);
            }else if ([type.lastObject isEqualToString:@"jpg"] || [type.lastObject isEqualToString:@"JPG"] || [type.lastObject isEqualToString:@"JPEG"] || [type.lastObject isEqualToString:@"jpeg"]){
                data = UIImageJPEGRepresentation(finalImage, 1);
            }else{
                data = UIImagePNGRepresentation(finalImage);
            }

压缩质量

// 压缩图片大小
+ (NSData *)compressImageQuality:(UIImage *)image toByte:(NSInteger)maxLength {
    CGFloat compression = 1;
    NSData *data = UIImageJPEGRepresentation(image, compression);
    if (data.length < maxLength) return data;
    CGFloat max = 1;
    CGFloat min = 0;
    for (int i = 0; i < 6; ++i) {
        compression = (max + min) / 2;
        data = UIImageJPEGRepresentation(image, compression);
        if (data.length < maxLength * 0.9) {
            min = compression;
        } else if (data.length > maxLength) {
            max = compression;
        } else {
            break;
        }
    }

    return data;
}

压缩质量和尺寸

+ (NSData *)compressImage:(UIImage *)image toByte:(NSUInteger)maxLength {
    // Compress by quality
    CGFloat compression = 1;
    NSData *data = UIImageJPEGRepresentation(image, compression);
    if (data.length < maxLength) return data;

    CGFloat max = 1;
    CGFloat min = 0;
    for (int i = 0; i < 6; ++i) {
        compression = (max + min) / 2;
        data = UIImageJPEGRepresentation(image, compression);
        if (data.length < maxLength * 0.9) {
            min = compression;
        } else if (data.length > maxLength) {
            max = compression;
        } else {
            break;
        }
    }
    UIImage *resultImage = [UIImage imageWithData:data];
    if (data.length < maxLength) return data;
    
    // Compress by size
    NSUInteger lastDataLength = 0;
    while (data.length > maxLength && data.length != lastDataLength) {
        lastDataLength = data.length;
        CGFloat ratio = (CGFloat)maxLength / data.length;
        CGSize size = CGSizeMake((NSUInteger)(resultImage.size.width * sqrtf(ratio)),
                                 (NSUInteger)(resultImage.size.height * sqrtf(ratio))); // Use NSUInteger to prevent white blank
        UIGraphicsBeginImageContext(size);
        [resultImage drawInRect:CGRectMake(0, 0, size.width, size.height)];
        resultImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        data = UIImageJPEGRepresentation(resultImage, compression);
    }
    return data;
}

后两压缩方法的来源地址