我们可以在不减小图片的分辨率（质量可以适当减小）的情况下，显著减小图片的大小
float kCompressionQuality = 0.3; // 具体大小自己调
NSData *photo = UIImageJPEGRepresentation(UIImage, kCompressionQuality);
上面方法等价于下面: 压缩图片质量
+(UIImage *)reduceImage:(UIImage *)image percent:(float)percent
{
NSData *imageData = UIImageJPEGRepresentation(image, percent);
UIImage *newImage = [UIImage imageWithData:imageData];
return newImage;
}
//将图片压缩到指定比例
-(UIImage *)scaleToSize:(UIImage *)aImage size:(CGSize)size{
//创建context,并将其设置为正在使用的context
UIGraphicsBeginImageContext(size);
//绘制出图片(大小已经改变)
[aImage drawInRect:CGRectMake(0, 0, size.width, size.height)];
//获取改变大小之后的图片
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
//context出栈
UIGraphicsEndImageContext();
return newImage; //返回获得的图片
}
等比例压缩
//等比例压缩
-(UIImage *)oldImage:(UIImage *)oldImage toSize:(CGSize)size{
UIImage *newImage = nil;//新照片对象
CGSize theSize = oldImage.size;//压缩前图片size
CGFloat width = theSize.width; //压缩前图片width
CGFloat height = theSize.height;//压缩前图片height
CGFloat newWidth = size.width; //压缩后图片width
CGFloat newHeight = size.height;//压缩后图片height
CGFloat scaleFactor = 0.0;//初值
CGFloat toWidth = newWidth;//压缩后图片width
CGFloat toHeight = newHeight;//压缩后图片height
CGPoint thumnailPoint = CGPointMake(0.0, 0.0);//给初值
if (CGSizeEqualToSize(theSize, size) == NO) {
//判断是不是已经满足 theSize = size 要求
CGFloat widthFac = newWidth/width;
CGFloat heithrFac = newHeight/height;
if (widthFac > heithrFac) {
scaleFactor = widthFac;
}else {
scaleFactor = heithrFac;
}
//不满足做等比例缩小处理
toWidth = width *scaleFactor;
toHeight = height *scaleFactor;
if (widthFac > heithrFac) {
thumnailPoint.y = (newHeight - toHeight)* 0.5;
}else if (widthFac < heithrFac){
thumnailPoint.x = (newWidth - toWidth)* 0.5;
}
}
//创建context,并将其设置为正在使用的context
UIGraphicsBeginImageContext(size);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumnailPoint;
thumbnailRect.size.width = toWidth;
thumbnailRect.size.height = toHeight;
//绘制出图片(大小已经改变)
[oldImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
//结果判断
if (newImage == nil) {
[NSException exceptionWithName:@"提示" reason:@"Error:image scale fail" userInfo:nil];
}
UIGraphicsEndImageContext();
return newImage;
}
-(UIImage *) imageCompressForWidth:(UIImage *)sourceImage targetWidth:(CGFloat)defineWidth{
UIImage *newImage = nil;
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
CGFloat targetWidth = defineWidth;
CGFloat targetHeight = height / (width / targetWidth);
CGSize size = CGSizeMake(targetWidth, targetHeight);
CGFloat scaleFactor = 0.0;
CGFloat scaledWidth = targetWidth;
CGFloat scaledHeight = targetHeight;
CGPoint thumbnailPoint = CGPointMake(0.0, 0.0);
if(CGSizeEqualToSize(imageSize, size) == NO){
CGFloat widthFactor = targetWidth / width;
CGFloat heightFactor = targetHeight / height;
if(widthFactor > heightFactor){
scaleFactor = widthFactor;
}
else{
scaleFactor = heightFactor;
}
scaledWidth = width * scaleFactor;
scaledHeight = height * scaleFactor;
if(widthFactor > heightFactor){
thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
}else if(widthFactor < heightFactor){
thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
}
}
UIGraphicsBeginImageContext(size);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
if(newImage == nil){
NSLog(@"scale image fail");
}
UIGraphicsEndImageContext();
return newImage;
}
图片的压缩其实是俩概念，
1、是 “压” 文件体积变小，但是像素数不变，长宽尺寸不变，那么质量可能下降，
2、是 “缩” 文件的尺寸变小，也就是像素数减少。长宽尺寸变小，文件体积同样会减小。
这个 UIImageJPEGRepresentation(image, 0.0)，是1的功能。
这个 [sourceImage drawInRect:CGRectMake(0,0,targetWidth, targetHeight)] 是2的功能。
所以，这俩你得结合使用来满足需求，不然你一味的用1，导致，图片模糊的不行，但是尺寸还是很大。
我们还可以对图片进行部分截取
-(UIImage*)getSubImage:(CGRect)rect
{
CGImageRefsubImageRef =CGImageCreateWithImageInRect(self.CGImage,rect);
CGRectsmallBounds =CGRectMake(0,0, CGImageGetWidth(subImageRef),CGImageGetHeight(subImageRef));
UIGraphicsBeginImageContext(smallBounds.size);
CGContextRefcontext =UIGraphicsGetCurrentContext();
CGContextDrawImage(context,smallBounds,subImageRef);
UIImage*smallImage =[UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();
returnsmallImage;
}
//--------------截取部分图片到指定位置-------------------------
图片(UIImage*)img
要截取的起始坐标sx:(int)sx1 sy:(int)sy1
要截取的长度和宽度sw:(int)sw1 sh:(int)sh1
最终要显示的坐标desx:(int)desx1 desy:(int)desy1
-(UIImage*)objectiveDrawRegion:(UIImage*)img sx:(int)sx1 sy:(int)sy1sw:(int)sw1 sh:(int)sh1 desx:(int)desx1 desy:(int)desy1{
[selfsaveImage:imgname:@"objectiveDrawRegion1.png"];
//创建图片缓冲
void*imageDataRegion=malloc(screenWidth*screenHeight*32);
CGColorSpaceRefiColorSpaceRegion=CGColorSpaceCreateDeviceRGB();
CGContextRefiDeviceRegion=CGBitmapContextCreate(imageDataRegion,screenWidth,screenHeight,8,4*screenWidth,iColorSpaceRegion,kCGImageAlphaPremultipliedLast);
//剪切区域
CGRectclipRegion=CGRectMake(sx1,sy1,sw1,sh1);
CGContextClipToRect(iDeviceRegion,clipRegion);
CGFloatwidthf=img.size.width;
CGFloatheightf=img.size.height;
CGRect cg=CGRectMake(0.0,0.0, widthf, heightf);
//画底图
CGContextDrawImage(iDeviceRegion,cg,img.CGImage);
//将缓冲形成图片
CGImageRefioffRegion=CGBitmapContextCreateImage(iDeviceRegion);
CGRect cg1=CGRectMake(desx1,desy1, sw1, sh1);
UIImage *ui=[UIImageimageWithCGImage:ioffRegion];
CGContextDrawImage(当前context,cg1,ui.CGImage);
//清除缓冲
CGColorSpaceRelease(iColorSpaceRegion);
CGContextRelease(iDeviceRegion);
CGImageRelease(ioffRegion);
free(imageDataRegion);
// iDeviceRegion=NULL;
// imageDataRegion=0;
returnui;
}
