Guennadi Liakhovetski | 35b23b5 | 2009-12-11 11:34:20 -0300 | [diff] [blame] | 1 | Cropping and Scaling algorithm, used in the sh_mobile_ceu_camera driver |
| 2 | ======================================================================= |
| 3 | |
| 4 | Terminology |
| 5 | ----------- |
| 6 | |
| 7 | sensor scales: horizontal and vertical scales, configured by the sensor driver |
| 8 | host scales: -"- host driver |
| 9 | combined scales: sensor_scale * host_scale |
| 10 | |
| 11 | |
| 12 | Generic scaling / cropping scheme |
| 13 | --------------------------------- |
| 14 | |
| 15 | -1-- |
| 16 | | |
| 17 | -2-- -\ |
| 18 | | --\ |
| 19 | | --\ |
| 20 | +-5-- -\ -- -3-- |
| 21 | | ---\ |
| 22 | | --- -4-- -\ |
| 23 | | -\ |
| 24 | | - -6-- |
| 25 | | |
| 26 | | - -6'- |
| 27 | | -/ |
| 28 | | --- -4'- -/ |
| 29 | | ---/ |
| 30 | +-5'- -/ |
| 31 | | -- -3'- |
| 32 | | --/ |
| 33 | | --/ |
| 34 | -2'- -/ |
| 35 | | |
| 36 | | |
| 37 | -1'- |
| 38 | |
| 39 | Produced by user requests: |
| 40 | |
| 41 | S_CROP(left / top = (5) - (1), width / height = (5') - (5)) |
| 42 | S_FMT(width / height = (6') - (6)) |
| 43 | |
| 44 | Here: |
| 45 | |
| 46 | (1) to (1') - whole max width or height |
| 47 | (1) to (2) - sensor cropped left or top |
| 48 | (2) to (2') - sensor cropped width or height |
| 49 | (3) to (3') - sensor scale |
| 50 | (3) to (4) - CEU cropped left or top |
| 51 | (4) to (4') - CEU cropped width or height |
| 52 | (5) to (5') - reverse sensor scale applied to CEU cropped width or height |
| 53 | (2) to (5) - reverse sensor scale applied to CEU cropped left or top |
| 54 | (6) to (6') - CEU scale - user window |
| 55 | |
| 56 | |
| 57 | S_FMT |
| 58 | ----- |
| 59 | |
| 60 | Do not touch input rectangle - it is already optimal. |
| 61 | |
| 62 | 1. Calculate current sensor scales: |
| 63 | |
| 64 | scale_s = ((3') - (3)) / ((2') - (2)) |
| 65 | |
| 66 | 2. Calculate "effective" input crop (sensor subwindow) - CEU crop scaled back at |
| 67 | current sensor scales onto input window - this is user S_CROP: |
| 68 | |
| 69 | width_u = (5') - (5) = ((4') - (4)) * scale_s |
| 70 | |
| 71 | 3. Calculate new combined scales from "effective" input window to requested user |
| 72 | window: |
| 73 | |
| 74 | scale_comb = width_u / ((6') - (6)) |
| 75 | |
| 76 | 4. Calculate sensor output window by applying combined scales to real input |
| 77 | window: |
| 78 | |
| 79 | width_s_out = ((2') - (2)) / scale_comb |
| 80 | |
| 81 | 5. Apply iterative sensor S_FMT for sensor output window. |
| 82 | |
| 83 | subdev->video_ops->s_fmt(.width = width_s_out) |
| 84 | |
| 85 | 6. Retrieve sensor output window (g_fmt) |
| 86 | |
| 87 | 7. Calculate new sensor scales: |
| 88 | |
| 89 | scale_s_new = ((3')_new - (3)_new) / ((2') - (2)) |
| 90 | |
| 91 | 8. Calculate new CEU crop - apply sensor scales to previously calculated |
| 92 | "effective" crop: |
| 93 | |
| 94 | width_ceu = (4')_new - (4)_new = width_u / scale_s_new |
| 95 | left_ceu = (4)_new - (3)_new = ((5) - (2)) / scale_s_new |
| 96 | |
| 97 | 9. Use CEU cropping to crop to the new window: |
| 98 | |
| 99 | ceu_crop(.width = width_ceu, .left = left_ceu) |
| 100 | |
| 101 | 10. Use CEU scaling to scale to the requested user window: |
| 102 | |
| 103 | scale_ceu = width_ceu / width |
| 104 | |
| 105 | |
| 106 | S_CROP |
| 107 | ------ |
| 108 | |
| 109 | If old scale applied to new crop is invalid produce nearest new scale possible |
| 110 | |
| 111 | 1. Calculate current combined scales. |
| 112 | |
| 113 | scale_comb = (((4') - (4)) / ((6') - (6))) * (((2') - (2)) / ((3') - (3))) |
| 114 | |
| 115 | 2. Apply iterative sensor S_CROP for new input window. |
| 116 | |
| 117 | 3. If old combined scales applied to new crop produce an impossible user window, |
| 118 | adjust scales to produce nearest possible window. |
| 119 | |
| 120 | width_u_out = ((5') - (5)) / scale_comb |
| 121 | |
| 122 | if (width_u_out > max) |
| 123 | scale_comb = ((5') - (5)) / max; |
| 124 | else if (width_u_out < min) |
| 125 | scale_comb = ((5') - (5)) / min; |
| 126 | |
| 127 | 4. Issue G_CROP to retrieve actual input window. |
| 128 | |
| 129 | 5. Using actual input window and calculated combined scales calculate sensor |
| 130 | target output window. |
| 131 | |
| 132 | width_s_out = ((3') - (3)) = ((2') - (2)) / scale_comb |
| 133 | |
| 134 | 6. Apply iterative S_FMT for new sensor target output window. |
| 135 | |
| 136 | 7. Issue G_FMT to retrieve the actual sensor output window. |
| 137 | |
| 138 | 8. Calculate sensor scales. |
| 139 | |
| 140 | scale_s = ((3') - (3)) / ((2') - (2)) |
| 141 | |
| 142 | 9. Calculate sensor output subwindow to be cropped on CEU by applying sensor |
| 143 | scales to the requested window. |
| 144 | |
| 145 | width_ceu = ((5') - (5)) / scale_s |
| 146 | |
| 147 | 10. Use CEU cropping for above calculated window. |
| 148 | |
| 149 | 11. Calculate CEU scales from sensor scales from results of (10) and user window |
| 150 | from (3) |
| 151 | |
| 152 | scale_ceu = calc_scale(((5') - (5)), &width_u_out) |
| 153 | |
| 154 | 12. Apply CEU scales. |
| 155 | |
| 156 | -- |
| 157 | Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de> |