我們可以在不減小圖片的分辨率（質(zhì)量可以適當(dāng)減小）的情況下翅雏，顯著減小圖片的大小
float kCompressionQuality = 0.3; // 具體大小自己調(diào)
NSData *photo = UIImageJPEGRepresentation(UIImage, kCompressionQuality);
上面方法等價于下面: 壓縮圖片質(zhì)量
+(UIImage *)reduceImage:(UIImage *)image percent:(float)percent
{
NSData *imageData = UIImageJPEGRepresentation(image, percent);
UIImage *newImage = [UIImage imageWithData:imageData];
return newImage;
}
//將圖片壓縮到指定比例
-(UIImage *)scaleToSize:(UIImage *)aImage size:(CGSize)size{
//創(chuàng)建context,并將其設(shè)置為正在使用的context
UIGraphicsBeginImageContext(size);
//繪制出圖片(大小已經(jīng)改變)
[aImage drawInRect:CGRectMake(0, 0, size.width, size.height)];
//獲取改變大小之后的圖片
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
//context出棧
UIGraphicsEndImageContext();
return newImage; //返回獲得的圖片
}
等比例壓縮
//等比例壓縮
-(UIImage *)oldImage:(UIImage *)oldImage toSize:(CGSize)size{
UIImage *newImage = nil;//新照片對象
CGSize theSize = oldImage.size;//壓縮前圖片size
CGFloat width = theSize.width; //壓縮前圖片width
CGFloat height = theSize.height;//壓縮前圖片height
CGFloat newWidth = size.width; //壓縮后圖片width
CGFloat newHeight = size.height;//壓縮后圖片height
CGFloat scaleFactor = 0.0;//初值
CGFloat toWidth = newWidth;//壓縮后圖片width
CGFloat toHeight = newHeight;//壓縮后圖片height
CGPoint thumnailPoint = CGPointMake(0.0, 0.0);//給初值
if (CGSizeEqualToSize(theSize, size) == NO) {
//判斷是不是已經(jīng)滿足 theSize = size 要求
CGFloat widthFac = newWidth/width;
CGFloat heithrFac = newHeight/height;
if (widthFac > heithrFac) {
scaleFactor = widthFac;
}else {
scaleFactor = heithrFac;
}
//不滿足做等比例縮小處理
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;
}
}
//創(chuàng)建context,并將其設(shè)置為正在使用的context
UIGraphicsBeginImageContext(size);
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumnailPoint;
thumbnailRect.size.width = toWidth;
thumbnailRect.size.height = toHeight;
//繪制出圖片(大小已經(jīng)改變)
[oldImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
//結(jié)果判斷
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;
}
圖片的壓縮其實是倆概念儡遮，
1、是 “壓” 文件體積變小嚼酝，但是像素數(shù)不變妄均，長寬尺寸不變，那么質(zhì)量可能下降倒堕，
2灾测、是 “縮” 文件的尺寸變小，也就是像素數(shù)減少垦巴。長寬尺寸變小媳搪，文件體積同樣會減小。
這個 UIImageJPEGRepresentation(image, 0.0)骤宣，是1的功能秦爆。
這個 [sourceImage drawInRect:CGRectMake(0,0,targetWidth, targetHeight)] 是2的功能。
所以憔披，這倆你得結(jié)合使用來滿足需求等限，不然你一味的用1，導(dǎo)致芬膝，圖片模糊的不行望门，但是尺寸還是很大。
我們還可以對圖片進(jìn)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;
}
//--------------截取部分圖片到指定位置-------------------------
圖片(UIImage*)img
要截取的起始坐標(biāo)sx:(int)sx1 sy:(int)sy1
要截取的長度和寬度sw:(int)sw1 sh:(int)sh1
最終要顯示的坐標(biāo)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"];
//創(chuàng)建圖片緩沖
void*imageDataRegion=malloc(screenWidth*screenHeight*32);
CGColorSpaceRefiColorSpaceRegion=CGColorSpaceCreateDeviceRGB();
CGContextRefiDeviceRegion=CGBitmapContextCreate(imageDataRegion,screenWidth,screenHeight,8,4*screenWidth,iColorSpaceRegion,kCGImageAlphaPremultipliedLast);
//剪切區(qū)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);
//畫底圖
CGContextDrawImage(iDeviceRegion,cg,img.CGImage);
//將緩沖形成圖片
CGImageRefioffRegion=CGBitmapContextCreateImage(iDeviceRegion);
CGRect cg1=CGRectMake(desx1,desy1, sw1, sh1);
UIImage *ui=[UIImageimageWithCGImage:ioffRegion];
CGContextDrawImage(當(dāng)前context,cg1,ui.CGImage);
//清除緩沖
CGColorSpaceRelease(iColorSpaceRegion);
CGContextRelease(iDeviceRegion);
CGImageRelease(ioffRegion);
free(imageDataRegion);
// iDeviceRegion=NULL;
// imageDataRegion=0;
returnui;
}
