How to use 9-patch images in IOS?
Solution 1:
Look into UIImage's method resizableImageWithCapInsets:(UIEdgeInsets)capInsets
.
Solution 2:
You can try this simple implementation: https://github.com/shiami/SWNinePatchImageFactory
The concept is easy and described as below:
The technique is only to transform the 9-patch PNG images to iOS compatible, resizable UIImage objects. See the UIImage's method resizableImageWithCapInsets:(UIEdgeInsets)insets for more info. So it only support to stretch one segment of patch markers in both horizontal and vertical sides.
+ (UIImage*)createResizableImageFromNinePatchImage:(UIImage*)ninePatchImage
{
NSArray* rgbaImage = [self getRGBAsFromImage:ninePatchImage atX:0 andY:0 count:ninePatchImage.size.width * ninePatchImage.size.height];
NSArray* topBarRgba = [rgbaImage subarrayWithRange:NSMakeRange(1, ninePatchImage.size.width - 2)];
NSMutableArray* leftBarRgba = [NSMutableArray arrayWithCapacity:0];
int count = [rgbaImage count];
for (int i = 0; i < count; i += ninePatchImage.size.width) {
[leftBarRgba addObject:rgbaImage[i]];
}
int top = -1, left = -1, bottom = -1, right = -1;
count = [topBarRgba count];
for (int i = 0; i <= count - 1; i++) {
NSArray* aColor = topBarRgba[i];
if ([aColor[3] floatValue] == 1) {
left = i;
break;
}
}
NSAssert(left != -1, @"The 9-patch PNG format is not correct.");
for (int i = count - 1; i >= 0; i--) {
NSArray* aColor = topBarRgba[i];
if ([aColor[3] floatValue] == 1) {
right = i;
break;
}
}
NSAssert(right != -1, @"The 9-patch PNG format is not correct.");
for (int i = left + 1; i <= right - 1; i++) {
NSArray* aColor = topBarRgba[i];
if ([aColor[3] floatValue] < 1) {
NSAssert(NO, @"The 9-patch PNG format is not support.");
}
}
count = [leftBarRgba count];
for (int i = 0; i <= count - 1; i++) {
NSArray* aColor = leftBarRgba[i];
if ([aColor[3] floatValue] == 1) {
top = i;
break;
}
}
NSAssert(top != -1, @"The 9-patch PNG format is not correct.");
for (int i = count - 1; i >= 0; i--) {
NSArray* aColor = leftBarRgba[i];
if ([aColor[3] floatValue] == 1) {
bottom = i;
break;
}
}
NSAssert(bottom != -1, @"The 9-patch PNG format is not correct.");
for (int i = top + 1; i <= bottom - 1; i++) {
NSArray* aColor = leftBarRgba[i];
if ([aColor[3] floatValue] == 0) {
NSAssert(NO, @"The 9-patch PNG format is not support.");
}
}
UIImage* cropImage = [ninePatchImage crop:CGRectMake(1, 1, ninePatchImage.size.width - 2, ninePatchImage.size.height - 2)];
return [cropImage resizableImageWithCapInsets:UIEdgeInsetsMake(top, left, bottom, right)];
}
SWNinePatchImageView also provides the Nib or Storyboard usage. You can check the example project in the repo.