ebiten/internal/graphics/math.go
Hajime Hoshi fd250c8d8c graphics: Rename NextPowerOf2Int -> InternalImageSize and add image size adjustment
There is a minimum internal image size on some system like old iOS
devices. This change adds adjustment of the size.

Issue: #810
2019-02-14 23:06:01 +09:00

47 lines
1.3 KiB
Go

// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package graphics
// minInternalImageSize is the minimum size of internal images (texture/framebuffer).
//
// For example, the image size less than 15 is not supported on some iOS devices.
// See also: https://stackoverflow.com/questions/15935651/certain-framebuffer-sizes-fail-on-ios-devices-gl-framebuffer-unsupported
const minInternalImageSize = 16
// InternalImageSize returns a nearest appropriate size as an internal image.
func InternalImageSize(x int) int {
if x <= 0 {
panic("graphics: x must be positive")
}
if x < minInternalImageSize {
return minInternalImageSize
}
r := 1
for r < x {
r <<= 1
}
return r
}
func isInternalImageSize(x int) bool {
if x <= 0 {
return false
}
if x < minInternalImageSize {
return false
}
return (x & (x - 1)) == 0
}